Work 2 the structure of the atom option 1. Chemistry (Structure of the atom) (presentation)

"The structure of the atom"

Option number 1

Exercise 1.

4d; 3p; 3d; 4s; 5s; 4p

Task 2.

Task 3.

11 cells Independent work No. 1

Option number 2

Exercise 1.

In what order will the sublevels be filled in:

4d; 3p; 3d; 4s; 5s; 4p

Task 2.

Task 3.

Determine the atoms of which elements have an electronic configuration:

a) 4s 2 4p 5 b) 3s 2 3p 6 3d 5 4s 2

11 cells Independent work No. 1

Option number 1

Exercise 1.

In what order will the sublevels be filled in:

4d; 3p; 3d; 4s; 5s; 4p

Exercise 2.

Construct the electronic and graphical configuration of argon and titanium atoms. What family do these elements belong to?

Task 3.

Determine the atoms of which elements have an electronic configuration:

a) 3s 2 3p 6 4s 2 b) 4s 2 4p 6 4d 1 5s 2

11 cells Independent work No. 1

Option number 2

Exercise 1.

In what order will the sublevels be filled in:

4d; 3p; 3d; 4s; 5s; 4p

Exercise 2.

Construct the electronic and graphical configuration of calcium and cobalt atoms. What family do these elements belong to?

Task 3.

Determine the atoms of which elements have an electronic configuration:

a) 4s 2 4p 5 b) 3s 2 3p 6 3d 5 4s

laboratory works

practical lessons

independent classroom work

independent homework (standard calculation)

control (defenses, colloquia, test, exam)

Textbooks and study guides

N.V. Korovin. general chemistry

General chemistry course. Theory and problems (under the editorship of N.V. Korovin, B.I. Adamson)

N.V. Korovin and others. Laboratory work in chemistry

Calendar plan

electrolytes,

Chemical equivalent

hydrolysis, PR

Electric form-

13(2 )

GE, electrolysis,

27(13,16)

14(2 )

corrosion

quantum number

17(2 )

18(2 )

Chemical bond

complexes

Thermodynamics

Kinetics.

6(2,3 )

Equilibrium

Introduction to Chemistry

Chemistry at the Energy Institute is a fundamental general theoretical discipline.

Chemistry is a natural science that studies the composition, structure, properties and transformations of substances, as well as the phenomena that accompany these transformations.

M.V. Lomonosov			D.I. Mendeleev
“Chemical
			"Fundamentals of Chemistry" 1871
considers	properties
			d.) – “Chemistry –
changes
			the doctrine of the elements and
explains
			their connections."
		chemical

transformations are taking place."

"Golden Age of Chemistry" (late XIX - early XX centuries)

Periodic law of D.I. Mendeleev (1896)

The concept of valency introduced by E. Frankland (1853)

Theory of the structure of organic compounds A.M.Butlerov (1861-1863)

Theory of complex compounds A. Werner

The law of mass action by M. Gultberg and L. Waage

Thermochemistry, developed mainly by G.I. Hess

Theory of electrolytic dissociation by S. Arrhenius

The principle of moving equilibrium by A. Le Chatelier

J.W. Gibbs phase rule

Theory of the complex structure of the atom Bohr-Sommerfeld (1913-1916)

Significance of the modern stage of development of chemistry

Understanding the laws of chemistry and their application allows you to create new processes, machines, installations and devices.

Obtaining electricity, fuel, metals, various materials, food, etc. directly related to chemical reactions. For example, electrical and mechanical energy is currently mainly obtained by converting the chemical energy of natural fuel (combustion reactions, the interaction of water and its impurities with metals, etc.). Without an understanding of these processes, it is impossible to ensure the efficient operation of power plants and internal combustion engines.

Knowledge of chemistry is necessary for:

- formation of scientific outlook,

- for the development of figurative thinking,

- creative growth of future specialists.

The modern stage in the development of chemistry is characterized by the widespread use of quantum (wave) mechanics for the interpretation and calculation of the chemical parameters of substances and systems of substances and is based on a quantum mechanical model of the structure of the atom.

An atom is a complex electromagnetic microsystem, which is the carrier of the properties of a chemical element.

STRUCTURE OF THE ATOM

Isotopes are varieties of atoms of the same chemical

elements that have the same atomic number but different atomic numbers

Mr (Cl) \u003d 35 * 0.7543 + 37 * 0.2457 \u003d 35.491

Fundamentals of quantum mechanics

Quantum mechanics- behavior of moving micro-objects (including electrons) is

the simultaneous manifestation of both the properties of particles and the properties of waves is a dual (corpuscular-wave) nature.

Energy quantization: Max Planck (1900, Germany) -

substances emit and absorb energy in discrete portions (quanta). The energy of a quantum is proportional to the frequency of radiation (oscillations) ν:

h is Planck's constant (6.626 10-34 J s); ν=с/λ , с – speed of light, λ – wavelength

Albert Einstein (1905): any radiation is a flux of energy quanta (photons) E = m v 2

Louis de Broglie (1924, France): electron is also characterizedcorpuscular-waveduality - radiation propagates like a wave and consists of small particles (photons)

		Particle - m,		mv , E=mv 2

	Wave - ,			E 2 \u003d h \u003d hv /
	Connected wavelength with mass and speed:
		E1 = E2;		h/mv
	uncertainty			Werner Heisenberg (1927,
Germany)		work	uncertainties		provisions
(coordinates)		particles x and	momentum (mv) not		May be

less than h/2

x (mv) h/2 (- error, uncertainty) I.e. the position and momentum of a particle cannot be determined in principle at any time with absolute accuracy.

Electron Cloud Atomic Orbital (AO)

That. the exact location of a particle (electron) is replaced by the concept of the statistical probability of finding it in a certain volume (near the nuclear) space.

The movement e- has a wave character and is described

2 dv is the probability density of finding e- in a certain volume near the nuclear space. This space is called atomic orbital (AO).

In 1926, Schrödinger proposed an equation that mathematically describes the state of e in an atom. Solving it

find the wave function. In a simple case, it depends on 3 coordinates

An electron carries a negative charge, its orbital represents a certain charge distribution and is called electron cloud

QUANTUM NUMBERS

Introduced to characterize the position of an electron in an atom in accordance with the Schrödinger equation

1. Principal quantum number(n)

Determines the energy of an electron - energy level

shows the size of the electron cloud (orbitals)

takes values from 1 to

n (energy level number): 1 2 3 4 etc.

2. Orbital quantum number(l) :

determines - the orbital angular momentum of the electron

shows the shape of the orbital

takes values - from 0 to (n -1)

Graphically, the AO is represented by the Orbital quantum number: 0 1 2 3 4

Energy sublevel: s p d f g

E increases


l=0	s-sublevel s-AO

	p-sublevel p-AO

Each n corresponds to a certain number of l values, i.e. each energy level is split into sublevels. The number of sublevels is equal to the level number.

1st energy level → 1 sublevel → 1s 2nd energy level → 2 sublevels → 2s2p 3rd energy level → 3 sublevels → 3s 3p 3d

4th energy level → 4 sublevels → 4s 4p 4d 4f etc.

3. Magnetic quantum number(ml)

defines – the value of the projection of the orbital angular momentum of the electron on an arbitrarily selected axis

shows - the spatial orientation of the AO

takes values – from –l to + l

Any value of l corresponds to (2l +1) values of the magnetic quantum number, i.e. (2l +1) possible locations of an electron cloud of a given type in space.

s - state - one orbital (2 0+1=1) - m l = 0, because l = 0

p - state - three orbitals (2 1+1=3)

m l : +1 0 -1, because l=1

ml =+1

m l =0

m l = -1

All orbitals belonging to the same sublevel have the same energy and are called degenerate.

Conclusion: AO is characterized by a certain set of n, l, m l , i.e. certain sizes, shape and orientation in space.

4. Spin quantum number (m s )

"spin" - "spindle"

determines - the intrinsic mechanical moment of an electron associated with its rotation around its axis

takes the values - (-1/2 h/2) or (+1/2 h/2)

n=3

l = 1

m l = -1, 0, +1

m s = + 1/2

Principles and rules

Electronic configurations of atoms

(in the form of electronic configuration formulas)

Indicate the numbers of the energy level number

The letters indicate the energy sublevel (s, p, d, f);

Sublevel exponent means number

electrons at a given sublevel

19 K 1s2 2s2 2p 6 3s 2 3p 6 4s 1

minimum

Electrons in an atom occupy the lowest energy state corresponding to its most stable state.

1s 2s 2p 3s 3p 3d 4s 4p 4d 4f

Increase E

Klechkovsky

Electrons are placed sequentially in orbitals characterized by an increase in the sum of the main and orbital quantum numbers (n + l) ; for the same values of this sum, the orbital with a lower value of the principal quantum number n is filled earlier

1s<2 s < 2 p = 3 s < 3 p = 4 s < 3 d = 4 p и т. д

Option 1

Part A.

A 1. The nucleus of an atom (39 K) is formed

1) 19 protons and 20 electrons 2) 20 neutrons and 19 electrons

3) 19 protons and 20 neutrons 4) 19 protons and 19 neutrons

A 2. The atom of the element phosphorus corresponds to the electronic formula

1) 1S 2 2S 2 2p 6 3S 2 3p 2 2) 1S 2 2S 2 2p 6 3S 2 3p 3 3) 1S 2 2S 2 2p 6 3S 2 3p 4 4) 1S 2 2S 2 2p 6 3S 2 3p 5

A 3. Chemical elements are arranged in order of decreasing their atomic radii

1) Ba, Cd, Sb 2) In, Pb, Sb 3) Cs, Na, H 4) Br, Se, As

A 4. Are the following statements about chemical elements correct?

A. All chemical elements-metals belong to S- and d-elements.

B. Non-metals in compounds exhibit only a negative oxidation state.

A 5. Among the metals of the main subgroup of group II, the most powerful reducing agent is

1) barium 2) calcium 3) strontium 4) magnesium

A 6. The number of energy layers and the number of electrons in the outer energy layer of the chromium atom are, respectively,

A 7. Higher chromium hydroxide exhibits

A 8. The electronegativity of elements increases from left to right in the series

1) O-S-Se-Te 2) B-Be-Li-Na 3) O-N-P-As 4) Ge-Si-S-Cl

A 9. The oxidation state of chlorine in Ba(ClO 3) 2 is

1) +1 2) +3 3) +5 4) +7

A 10. The element arsenic belongs to

Answers to the task B1-B2

IN 1. The increase in the acidic properties of higher oxides occurs in the series:

1) CaOSiO 2 SO 3 2) CO 2 Al 2 O 3 MgO 3) Li 2 OCO 2 N 2 O 5

4) As 2 O 5 P 2 O 5 N 2 O 5 5) BeOCaOSrO 6) SO 3 P 2 O 5 Al 2 O 3

AT 2. Set a match.

Core Composition Electronic formula

A. 7 p + 1, 7 n 0 1 1. 2S 2 2p 3

B. 15 p + 1, 16 n 0 1 2. 2S 2 2p 4

B. 9 p + 1 , 10 n 0 1 3. 3S 2 3p 5

D. 34 p + 1, 45 n 0 1 4. 2S 2 2p 5

From 1. Write the formula for the higher oxide and higher bromine hydroxide. Write down the electronic configuration of the bromine atom in the ground and excited state, determine its possible valencies.

Write the electronic formulas of the bromine atom in the maximum and minimum powers.

Examination No. 1 on the topic "Structure of the atom"

Option 2

Part A. Choose one correct answer

A 1. The number of protons, neutrons and electrons of the 90 Sr isotope, respectively, is

1. 38, 90, 38 2. 38, 52, 38 3. 90, 52, 38 4. 38, 52,90

A 2. The electronic formula 1S 2 2S 2 2p 6 3S 2 3p 6 4S 1 corresponds to the atom of the element

1. sulfur 2. bromine 3. potassium 4. manganese

A 3. Elements are arranged in order of decreasing atomic radius

1) boron, aluminum, gallium 3) boron, carbon, silicon

2) potassium, sodium, lithium 4) krypton, xenon, radon

A 4. Are the following judgments about changing the properties of elements in a series correct?

Be-Mg-Ca-Sr-Ba?

A. Metallic properties are enhanced.

B. The radius of atoms and the number of valence electrons do not change.

1) only A is true 2) only B is true 3) both judgments are correct 4) both judgments are wrong

A 5. Among the non-metals of the third period, the most powerful oxidizing agent is

1) phosphorus 2) silicon 3) sulfur 4) chlorine

A 6. The number of energy layers and the number of electrons in the outer energy layer of a manganese atom are, respectively,

1) 4, 2 2) 4, 1 3) 4, 6 4) 4, 5

A 7. Higher manganese hydroxide exhibits

1) acidic properties 3) basic properties

2) amphoteric properties 4) does not show acid-base properties

A 8. The electronegativity of elements decreases from left to right along the row

1) O-Se-S-Te 2) Be-Be-Li-H 3) O-N-P-As 4) Ge-Si-S-Cl

A 9. The oxidation state of nitrogen in Ba(NO 2) 2 is

1) +1 2) +3 3) +5 4) +7

A 10. The element manganese belongs to

1) s-elements 2) p-elements 3) d-elements 4) transition elements

Answers to the task B1-B2 is the sequence of digits that corresponds to the numbers of the correct answers.

IN 1. The increase in the basic properties of higher hydroxides occurs in the series of the elements that form them:

1) MgAl ) AsР 3) PSCl

4) BBeLi 5) MgCaBa 6)CaKCs

AT 2. Set a match.

Core Composition Electronic formula

A. 19 p + 1, 20 n 0 1 1. 4S 1

B. 20 p + 1, 20 n 0 1 2. 4S 2

B. 14 p + 1, 14 n 0 1 3. 5S 1

D. 35 p + 1, 45 n 0 1 4. 4S 2 4p 5

When completing task C 1, write down in detail the course of its solution and the result obtained.

From 1. Write the formula for the higher oxide and higher arsenic hydroxide. Write down the electronic configuration of the arsenic atom in the ground and excited state, determine its possible valencies.

Write the electronic formulas of the arsenic atom in the maximum and minimum powers.

CONTROL WORK No. 1 Theme "Structure of the atom" Grade 11

Option 1

1. The number of the period in the Periodic system is determined by:

A. The charge of the nucleus of an atom

B. The number of electrons in the outer layer of the atom.

B. The number of electron layers in an atom

D. The number of electrons in an atom.

A. S and Cl B. Be and B C. Kr and Xe D. Mo and Se

3. p - The element is:

A. Scandium.

B. Barium.

B. Arsenic

G. Helium

10 4s 2 matches the element:

A. Calcium.

B. Krypton.

V. Cadmium.

G. Zincu.

A. Zn(OH) 2

B. Mg(OH) 2

B. Ca (OH) 2

D. Cr(OH) 2

A. Mg - Ca - Zn.

B.Al - Mg - Ca.

B.Sr - Rb - K.

G.Ge - Si - Sb.

2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 1

A.E 2 O

B.E 2 O 3

V.EO 2

G.EO 3

8. An isotope of calcium, the nucleus of which contains 22 neutrons, is denoted:

A. 20 40 Ca

B. 20 42 CaV. 20 44 Ca

G. 20 48 Sa

9. Match:

Element:

Aluminum. II. Potassium. III. Selenium. IV. Magnesium.

Electronic formula:

A.1s 2 2s 2 2p 6 3s 2 3p 1

B.1s 2 2s 2 2p 6 3s 2

B.1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 4

D.1s 2 2s 2 3s 2 3p 6 4s 1

Superior Oxide Formula:

E 2 O 2.E 2 O 3 3.EO 4.EO 3

Higher hydroxide formula:

A. EON. b. E(OH) 2 . V. E(OH) 3 g. H 2 EO 4

10. Based on the position in the Periodic system, arrange the elements: germanium, arsenic, sulfur, phosphorus - in descending order of oxidizing properties. Explain the answer.

11. How and why do metallic properties change in the Periodic Table?

A. Within a period.

B. Within the main subgroup.

12. Make an electronic formula for the element with serial number 30 in the Periodic system. Make a conclusion about whether this element belongs to metals or non-metals. Write down the formulas of its higher oxide and hydroxide, indicate their nature.

13. What chemical properties are characteristic of the highest oxide of the element of the 3rd period, the main subgroup of the VI group of the Periodic system? Support your answer by writing the reaction equations.

Test No. 1 Theme "Structure of the atom" Grade 11

Option 2

The group number (for elements of the main subgroups) in the Periodic system determines:

A. The number of protons in an atom.

B. The number of electrons in the outer layer of the atom.

B. The number of electron layers in an atom.

D. The number of neutrons in an atom.

2. A pair of elements with a similar structure of the outer and pre-outer energy levels:

A.Ba and K B.Ti and Ge

B.Sb and Bi G.Kr and Fe

3. p - The element is:

A.Kaliy

B. Silicon

V.Argon

G.Copper

4. Electronic configuration. . .3d 5 4s 2 matches the element:

A. Broma

B. Calcium

V. manganese

G. chlorine

5. Amphoteric oxide is a substance whose formula is:

A. CrO B.Cr 2 O 3 C. CrO 3 D. FeO

6. A number of elements, arranged in order of strengthening the metallic properties:

A. Al - Ga - Ge.

B. Ca-Sr-Ba.

B. K-Na-Li.

G. Mg - Ca - Zn.

7.Element E with the electronic formula 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 3 a higher oxide is formed, corresponding to the formula:

A.EO

B.E 2 O 3

V.E 2 O 5

G.EO 3

8. An isotope of iron, the nucleus of which contains 30 neutrons, denote:

A. 26 54 Fe

B. 26 56 Fe

B. 26 57 Fe

D. 26 58 Fe

9. Match:

Element:

Bor. II. Bromine. III. Phosphorus. IV. Lithium.

Electronic formula:

A.1s 2 2s 2 2p 1

B.1s 2 2s 1

B. 1s 2 2s 2 2p 6 3s 2 3p 3

D. 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 5

Superior Oxide Formula:

E 2 O 2.E 2 O 3 3.E 2 O 5 4.E 2 O 7

Higher hydroxide formula:

A. EON. b. NET 3 . V. N 3 EO 3 g. NET 4

PART B. Assignments with free answer

10. Based on the position in the Periodic system, arrange the elements: aluminum, potassium, calcium, magnesium - in ascending order of reducing properties. Explain the answer.

11. Why do the charges of the nuclei of the atoms of the elements, arranged in ascending order of serial numbers in the Periodic system, change monotonously, and the properties of the elements - periodically?

12. Make an electronic formula of the element with serial number 38 in the Periodic system. Make a conclusion about whether this element belongs to metals or non-metals. Write down the formulas of its higher oxide and hydroxide, indicate their nature.

13. What chemical properties are characteristic of metal hydroxides? Support your answer by writing the reaction equations.

Option 3

1. The total number of electrons in an atom of an element is determined using the Periodic system, by number:

A. Groups.

B. Period.

V. Row.

G. Order.

2. A pair of elements with a similar structure of the outer and pre-outer energy levels:

A. Sn and Si B. As and Se C. Zn and Ca D. Mo and Te

3. f - The element is:

A. Germanium.

B. Potassium.

V. Selenium.

G. Uranus.

4. Electronic configuration. . .4s 24p6 matches the element:

A. Brom.

B. Iron.

V. Neon.

G. Krypton.

5. Amphoteric hydroxide is a substance whose formula is:

A. Ga(OH) 3.

B. Mg(OH) 2.

B. LiOH.

D. Sc(OH) 2

6. A number of elements, arranged in order of strengthening the metallic properties:

A. K - Rb - Sr.

B.Al - Mg - Ca.

B. Be - Li - Cs.

G.Ge - Sn - Sb.

7.Element E with the electronic formula 1s 2 2s 2 2p 6 3s 1 a higher oxide is formed, corresponding to the formula:

A.E 2 O

B.E 2 O 3

V.EO 2

G.EO 3

8. An isotope of calcium, the nucleus of which contains 24 neutrons, is denoted:

A. 20 40 Ca

B. 20 42 Sa

B. 20 44 Ca

G. 20 48 Sa

9. Match:

Element:

Nitrogen. II. Calcium. III. Silicon. IV. Sulfur.

Electronic formula:

A.1s 2 2s 2 2p 3

B.1s 2 2s 2 2p 6 3s 2 3p 4

B.1s 2 2s 2 2p 6 3s 2 3p 2

D.1s 2 2s 2 3s 2 3p 6 4s 2

Superior Oxide Formula:

EO 2.EO 2 3.E 2 O 5 4.EO 3

Higher hydroxide formula:

A. H 2 OE 4 . b. E(OH) 2 . V. N 2 EO 3 g. NET 3

PART B. Assignments with free answer

10. Based on the position in the Periodic system, arrange the elements: oxygen, arsenic, sulfur, phosphorus - in descending order of oxidizing properties. Explain the answer.

11. List the basic rules (laws), according to which the levels, sublevels and orbitals are filled with electrons in the electron shell of the atoms of elements.

12. Make an electronic formula of the element with serial number 34 in the Periodic system. Make a conclusion about whether this element belongs to metals or non-metals. Write down the formulas of its higher oxide and hydroxide, indicate their nature.

13. What chemical properties are characteristic of non-metal hydroxides? Support your answer by writing the reaction equations.

Electrons

The concept of an atom originated in the ancient world to denote the particles of matter. In Greek, atom means "indivisible".

The Irish physicist Stoney, on the basis of experiments, came to the conclusion that electricity is carried by the smallest particles that exist in the atoms of all chemical elements. In 1891, Stoney proposed to call these particles electrons, which in Greek means "amber". A few years after the electron got its name, English physicist Joseph Thomson and French physicist Jean Perrin proved that electrons carry a negative charge. This is the smallest negative charge, which in chemistry is taken as a unit (-1). Thomson even managed to determine the speed of the electron (the speed of an electron in orbit is inversely proportional to the orbit number n. The radii of the orbits grow in proportion to the square of the orbit number. In the first orbit of the hydrogen atom (n=1; Z=1), the speed is ≈ 2.2 106 m / c, that is, about a hundred times less than the speed of light c=3 108 m/s.) and the mass of an electron (it is almost 2000 times less than the mass of a hydrogen atom).

The state of electrons in an atom

The state of an electron in an atom is a set of information about the energy of a particular electron and the space in which it is located. An electron in an atom does not have a trajectory of motion, i.e., one can only speak of the probability of finding it in the space around the nucleus.

It can be located in any part of this space surrounding the nucleus, and the totality of its various positions is considered as an electron cloud with a certain negative charge density. Figuratively, this can be imagined as follows: if it were possible to photograph the position of an electron in an atom in hundredths or millionths of a second, as in a photo finish, then the electron in such photographs would be represented as points. Overlaying countless such photographs would result in a picture of an electron cloud with the highest density where there will be most of these points.

The space around the atomic nucleus, in which the electron is most likely to be found, is called the orbital. It contains approximately 90% e-cloud, and this means that about 90% of the time the electron is in this part of space. Distinguished by shape 4 currently known types of orbitals, which are denoted by Latin letters s, p, d and f. A graphic representation of some forms of electronic orbitals is shown in the figure.

The most important characteristic of the motion of an electron in a certain orbit is the energy of its connection with the nucleus. Electrons with similar energy values form a single electron layer, or energy level. Energy levels are numbered starting from the nucleus - 1, 2, 3, 4, 5, 6 and 7.

An integer n, denoting the number of the energy level, is called the main quantum number. It characterizes the energy of electrons occupying a given energy level. The electrons of the first energy level, closest to the nucleus, have the lowest energy. Compared with the electrons of the first level, the electrons of the next levels will be characterized by a large amount of energy. Consequently, the electrons of the outer level are the least strongly bound to the nucleus of the atom.

The largest number of electrons in the energy level is determined by the formula:

N = 2n2,

where N is the maximum number of electrons; n is the level number, or the main quantum number. Consequently, the first energy level closest to the nucleus can contain no more than two electrons; on the second - no more than 8; on the third - no more than 18; on the fourth - no more than 32.

Starting from the second energy level (n = 2), each of the levels is subdivided into sublevels (sublayers), which differ somewhat from each other in the binding energy with the nucleus. The number of sublevels is equal to the value of the main quantum number: the first energy level has one sublevel; the second - two; third - three; fourth - four sublevels. Sublevels, in turn, are formed by orbitals. Each valuen corresponds to the number of orbitals equal to n.

It is customary to designate sublevels in Latin letters, as well as the shape of the orbitals of which they consist: s, p, d, f.

Protons and neutrons

An atom of any chemical element is comparable to a tiny solar system. Therefore, such a model of the atom, proposed by E. Rutherford, is called planetary.

The atomic nucleus, in which the entire mass of the atom is concentrated, consists of particles of two types - protons and neutrons.

Protons have a charge equal to the charge of electrons, but opposite in sign (+1), and a mass equal to the mass of a hydrogen atom (it is accepted in chemistry as a unit). Neutrons carry no charge, they are neutral and have a mass equal to that of a proton.

Protons and neutrons are collectively called nucleons (from the Latin nucleus - nucleus). The sum of the number of protons and neutrons in an atom is called the mass number. For example, the mass number of an aluminum atom:

13 + 14 = 27

number of protons 13, number of neutrons 14, mass number 27

Since the mass of the electron, which is negligible, can be neglected, it is obvious that the entire mass of the atom is concentrated in the nucleus. Electrons represent e - .

Because the atom electrically neutral, it is also obvious that the number of protons and electrons in an atom is the same. It is equal to the serial number of the chemical element assigned to it in the Periodic system. The mass of an atom is made up of the mass of protons and neutrons. Knowing the serial number of the element (Z), i.e., the number of protons, and the mass number (A), equal to the sum of the numbers of protons and neutrons, you can find the number of neutrons (N) using the formula:

N=A-Z

For example, the number of neutrons in an iron atom is:

56 — 26 = 30

isotopes

Varieties of atoms of the same element that have the same nuclear charge but different mass numbers are called isotopes. Chemical elements found in nature are a mixture of isotopes. So, carbon has three isotopes with a mass of 12, 13, 14; oxygen - three isotopes with a mass of 16, 17, 18, etc. The relative atomic mass of a chemical element usually given in the Periodic System is the average value of the atomic masses of a natural mixture of isotopes of a given element, taking into account their relative content in nature. The chemical properties of the isotopes of most chemical elements are exactly the same. However, hydrogen isotopes differ greatly in properties due to the dramatic fold increase in their relative atomic mass; they have even been given individual names and chemical symbols.

Elements of the first period

Scheme of the electronic structure of the hydrogen atom:

Schemes of the electronic structure of atoms show the distribution of electrons over electronic layers (energy levels).

The graphical electronic formula of the hydrogen atom (shows the distribution of electrons over energy levels and sublevels):

Graphic electronic formulas of atoms show the distribution of electrons not only in levels and sublevels, but also in orbits.

In a helium atom, the first electron layer is completed - it has 2 electrons. Hydrogen and helium are s-elements; for these atoms, the s-orbital is filled with electrons.

All elements of the second period the first electron layer is filled, and the electrons fill the s- and p-orbitals of the second electron layer in accordance with the principle of least energy (first s, and then p) and the rules of Pauli and Hund.

In the neon atom, the second electron layer is completed - it has 8 electrons.

For atoms of elements of the third period, the first and second electron layers are completed, so the third electron layer is filled, in which electrons can occupy 3s-, 3p- and 3d-sublevels.

A 3s electron orbital is completed at the magnesium atom. Na and Mg are s-elements.

For aluminum and subsequent elements, the 3p sublevel is filled with electrons.

The elements of the third period have unfilled 3d orbitals.

All elements from Al to Ar are p-elements. s- and p-elements form the main subgroups in the Periodic system.

Elements of the fourth - seventh periods

A fourth electron layer appears at the potassium and calcium atoms, the 4s sublevel is filled, since it has less energy than the 3d sublevel.

K, Ca - s-elements included in the main subgroups. For atoms from Sc to Zn, the 3d sublevel is filled with electrons. These are 3d elements. They are included in the secondary subgroups, they have a pre-external electron layer filled, they are referred to as transition elements.

Pay attention to the structure of the electron shells of chromium and copper atoms. In them, a “failure” of one electron from the 4s- to the 3d-sublevel occurs, which is explained by the greater energy stability of the resulting electronic configurations 3d 5 and 3d 10:

In the zinc atom, the third electron layer is completed - all the 3s, 3p and 3d sublevels are filled in it, in total there are 18 electrons on them. In the elements following zinc, the fourth electron layer continues to be filled, the 4p sublevel.

Elements from Ga to Kr are p-elements.

The outer layer (fourth) of the krypton atom is complete and has 8 electrons. But there can only be 32 electrons in the fourth electron layer; the 4d- and 4f-sublevels of the krypton atom still remain unfilled. The elements of the fifth period are filling the sub-levels in the following order: 5s - 4d - 5p. And there are also exceptions related to " failure» electrons, y 41 Nb, 42 Mo, 44 Ru, 45 Rh, 46 Pd, 47 Ag.

In the sixth and seventh periods, f-elements appear, i.e., elements in which the 4f- and 5f-sublevels of the third outer electronic layer are filled, respectively.

4f elements are called lanthanides.

5f elements are called actinides.

The order of filling of electronic sublevels in the atoms of elements of the sixth period: 55 Cs and 56 Ba - 6s-elements; 57 La … 6s 2 5d x - 5d element; 58 Ce - 71 Lu - 4f elements; 72 Hf - 80 Hg - 5d elements; 81 T1 - 86 Rn - 6d elements. But even here there are elements in which the order of filling of electronic orbitals is “violated”, which, for example, is associated with greater energy stability of half and completely filled f-sublevels, i.e. nf 7 and nf 14. Depending on which sublevel of the atom is filled with electrons last, all elements are divided into four electronic families, or blocks:

s-elements. The s-sublevel of the outer level of the atom is filled with electrons; s-elements include hydrogen, helium and elements of the main subgroups of groups I and II.

p-elements. The p-sublevel of the outer level of the atom is filled with electrons; p-elements include elements of the main subgroups of III-VIII groups.

d-elements. The d-sublevel of the preexternal level of the atom is filled with electrons; d-elements include elements of secondary subgroups of groups I-VIII, i.e., elements of intercalary decades of large periods located between s- and p-elements. They are also called transition elements.

f-elements. The f-sublevel of the third outside level of the atom is filled with electrons; these include the lanthanides and antinoids.

The Swiss physicist W. Pauli in 1925 established that in an atom in one orbital there can be no more than two electrons having opposite (antiparallel) spins (translated from English - “spindle”), i.e. having such properties that can be conditionally imagined as the rotation of an electron around its imaginary axis: clockwise or counterclockwise.

This principle is called Pauli principle. If there is one electron in the orbital, then it is called unpaired, if there are two, then these are paired electrons, that is, electrons with opposite spins. The figure shows a diagram of the division of energy levels into sublevels and the order in which they are filled.

Very often, the structure of the electron shells of atoms is depicted using energy or quantum cells - they write down the so-called graphic electronic formulas. For this record, the following notation is used: each quantum cell is denoted by a cell that corresponds to one orbital; each electron is indicated by an arrow corresponding to the direction of the spin. When writing a graphical electronic formula, two rules should be remembered: Pauli principle and F. Hund's rule, according to which electrons occupy free cells, first one at a time and at the same time have the same spin value, and only then pair, but the spins, according to the Pauli principle, will already be oppositely directed.

Hund's rule and Pauli's principle

Hund's rule- the rule of quantum chemistry, which determines the order of filling the orbitals of a certain sublayer and is formulated as follows: the total value of the spin quantum number of electrons of this sublayer should be maximum. Formulated by Friedrich Hund in 1925.

This means that in each of the orbitals of the sublayer, one electron is first filled, and only after the unfilled orbitals are exhausted, a second electron is added to this orbital. In this case, there are two electrons with half-integer spins of the opposite sign in one orbital, which pair (form a two-electron cloud) and, as a result, the total spin of the orbital becomes equal to zero.

Other wording: Below in energy lies the atomic term for which two conditions are satisfied.

Multiplicity is maximum
When the multiplicities coincide, the total orbital momentum L is maximum.

Let's analyze this rule using the example of filling the orbitals of the p-sublevel p- elements of the second period (that is, from boron to neon (in the diagram below, horizontal lines indicate orbitals, vertical arrows indicate electrons, and the direction of the arrow indicates the orientation of the spin).

Klechkovsky's rule

Klechkovsky's rule - as the total number of electrons in atoms increases (with an increase in the charges of their nuclei, or the ordinal numbers of chemical elements), atomic orbitals are populated in such a way that the appearance of electrons in higher-energy orbitals depends only on the principal quantum number n and does not depend on all other quantum numbers. numbers, including those from l. Physically, this means that in a hydrogen-like atom (in the absence of interelectron repulsion) the orbital energy of an electron is determined only by the spatial remoteness of the electron charge density from the nucleus and does not depend on the features of its motion in the field of the nucleus.

Klechkovsky's empirical rule and the sequence of sequences of a somewhat contradictory real energy sequence of atomic orbitals arising from it only in two cases of the same type: for atoms Cr, Cu, Nb, Mo, Ru, Rh, Pd, Ag, Pt, Au, there is a “failure” of an electron with s - sublevel of the outer layer to the d-sublevel of the previous layer, which leads to an energetically more stable state of the atom, namely: after filling the orbital 6 with two electrons s