How to determine s p d f elements. S-, p-, d- and f-elements. Difference between amphoteric oxides and basic and acidic oxides. Ionic-molecular and molecular equations of joint hydrolysis. Biological role of macro- and microelements
Exercise 1
1) D.I.Mendeleev’s periodic law, its modern formulation. 2) The structure of the periodic system from the point of view of the structure of the atom. 3) The periodicity of changes in the properties of the atom: ionization energy, electronegativity, energy means to the electron. 4) Main classes of chemical compounds. 5) Classification of biogenic elements. 6) Qualitative and quantitative content of macro- and microelements in the human body. 7) Elements are organogens.
Periodic law- a fundamental law of nature, discovered by D.I. Mendeleev in 1869 when comparing the properties of chemical elements known at that time and the values of their atomic masses.
The formulation of the periodic law given by D.I. Mendeleev, said: the properties of chemical elements are periodically dependent on the atomic masses of these elements. The modern formulation states: the properties of chemical elements are periodically dependent on the charge of the nucleus of these elements. Such clarification was required because at the time Mendeleev established the periodic law, the structure of the atom was not yet known. After elucidating the structure of the atom and establishing the patterns of electron placement in electronic levels, it became clear that the periodic repeatability of the properties of elements is associated with the repeatability of the structure of electronic shells.
Periodic table– a graphic representation of the periodic law, the essence of which is that with an increase in the charge of the nucleus, the structure of the electronic shell of atoms periodically repeats, which means that the properties of chemical elements and their compounds will periodically change.
The properties of elements, as well as the forms and properties of compounds of elements, periodically depend on the charges of nuclei and atoms.
Ionization energy– a type of binding energy, represents the smallest energy required to remove an electron from a free atom in its lowest energy (ground) state to infinity.
Ionization energy is one of the main characteristics of an atom, on which the nature and strength of the chemical bonds formed by the atom largely depend. The reducing properties of the corresponding simple substance also significantly depend on the ionization energy of the atom. The ionization energy of elements is measured in electronvolts per atom or joules per mole.
Electron affinity- energy that is released or absorbed due to the addition of an electron to an isolated atom in a gaseous state. Expressed in kilojoules per mole (kJ/mol) or electron volts (eV). It depends on the same factors as ionization energy.
Electronegativity- the relative ability of the atoms of an element to attract electrons to themselves in any environment. It directly depends on the radius or size of the atom. The smaller the radius, the more strongly it will attract electrons from another atom. Therefore, the higher and more to the right an element is in the periodic table, the smaller its radius and the greater its electronegativity. Essentially, electronegativity determines the type of chemical bond.
Chemical compound- a complex substance consisting of chemically bonded atoms of two or more elements. They are divided into classes: inorganic and organic.
Organic compounds– a class of chemical compounds that contain carbon (there are exceptions). The main groups of organic compounds: hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, amides, amines.
Inorganic compounds– a chemical compound that is not organic, that is, it does not contain carbon. Inorganic compounds do not have the carbon skeleton characteristic of organic compounds. They are divided into simple and complex (oxides, bases, acids, salts).
Chemical element– a collection of atoms with the same nuclear charge and number of protons, coinciding with the serial (atomic) number in the periodic table. Each chemical element has its own Latin name and chemical symbol, consisting of one or a pair of Latin letters, regulated by IUPAC and listed in the table of Mendeleev’s Periodic Table of Elements.
More than 70 elements have been found in living matter.
Nutrients- elements necessary for the body to build and function cells and organs. There are several classifications of nutrients:
A) According to their functional role:
1) organogens, 97% of them in the body (C, H, O, N, P, S);
2) elements of the electrolyte background (Na, K, Ca, Mg, Cl). These metal ions account for 99% of the total metal content in the body;
3) microelements - biologically active atoms of the centers of enzymes and hormones (transition metals).
B) According to the concentration of elements in the body:
1) macroelements – content exceeds 0.01% of body weight (Fe, Zn, I, Cu, Mn, Cr, F, Mo, Co, Ni, B, V, Si, Al, Ti, Sr, Se, Rb, Li)
2) microelements – the content is about 0.01%. Most are found primarily in liver tissue. Some microelements show affinity for certain tissues (iodine - to the thyroid gland, fluorine - to tooth enamel, zinc - to the pancreas, molybdenum - to the kidneys). (Ca, Mg, Na, K, P, Cl, S).
3) ultramicroelements – content less than 10-5%. Data on the quantity and biological role of many elements have not been fully identified.
Microelements depot organs:
Fe - Accumulates in red blood cells, spleen, liver
K - Accumulates in the heart, skeletal and smooth muscles, blood plasma, nervous tissue, kidneys.
Mn - depot organs: bones, liver, pituitary gland.
P - depot organs: bones, protein substances.
Ca - depot organs: bones, blood, teeth.
Zn - depot organs: liver, prostate, retina.
I - Depot organs: thyroid gland.
Si - depot organs: liver, hair, eye lens.
Mg - depot organs: biological fluids, liver
Cu - storage organs: bones, liver, gall bladder
S - depot organs: connective tissue
Ni - depot organs: lungs, liver, kidneys, pancreas, blood plasma.
Biological role of macro- and microelements:
Fe - participates in hematopoiesis, respiration, immunobiological and redox reactions. With a deficiency, anemia develops.
K - participates in urination, the occurrence of action potentials, maintaining osmotic pressure, protein synthesis.
Mn - Affects the development of the skeleton, participates in immune reactions, hematopoiesis and tissue respiration.
P - combines consecutive nucleotides in the DNA and RNA strands. ATP serves as the main energy carrier of cells. Forms cell membranes. The strength of bones is determined by the presence of phosphates in them.
Ca - participates in the occurrence of nervous excitation, in the coagulation functions of the blood, and provides osmotic pressure of the blood.
Co - Tissues in which the microelement usually accumulates: blood, spleen, bone, ovaries, liver, pituitary gland. Stimulates hematopoiesis, participates in protein synthesis and carbohydrate metabolism.
Zn - participates in hematopoiesis, participates in the activity of endocrine glands.
I - Necessary for the normal functioning of the thyroid gland, affects mental abilities.
Si - promotes collagen synthesis and the formation of cartilage tissue.
Mg - participates in various metabolic reactions: synthesis of enzymes, proteins, etc. coenzyme for the synthesis of B vitamins.
Cu - Affects the synthesis of hemoglobin, red blood cells, proteins, the coenzyme for the synthesis of B vitamins.
S - Affects the condition of the skin.
Ag - Antimicrobial activity
Ni - stimulates the synthesis of amino acids in the cell, increases the activity of pepsin, normalizes hemoglobin content, improves the generation of plasma proteins.
Organogenic elements- chemical elements that form the basis of organic compounds (C, H, O, N, S, P). In biology, four elements are called organogenic, which together make up about 96-98% of the mass of living cells (C, H, O, N).
Carbon- the most important chemical element for organic compounds. Organic compounds by definition are compounds of carbon. It is tetravalent and is capable of forming strong covalent bonds with each other.
Role hydrogen in organic compounds mainly consists of binding those electrons of carbon atoms that do not participate in the formation of intercarbon bonds in the composition of polymers. However, hydrogen is involved in the formation of non-covalent hydrogen bonds.
Together with carbon and hydrogen, oxygen is included in many organic compounds as part of such functional groups as hydroxyl, carbonyl, carboxyl and the like.
Nitrogen often included in organic substances in the form of an amino group or heterocycle. It is a mandatory chemical element in the composition. Nitrogen is also part of nitrogenous bases, the residues of which are contained in nucleosides and nucleotides.
Sulfur is part of some amino acids, in particular methionine and cysteine. In proteins, disulfide bonds are established between the sulfur atoms of cysteine residues, ensuring the formation of a tertiary structure.
Phosphate groups, that is, orthophosphoric acid residues are part of such organic substances as nucleotides, nucleic acids, phospholipids, phosphoproteins.
Task 2,3,4
Biogenic s- and p-elements. Relationship between the electronic structure of s- and p-elements and their biological functions. Compounds s- and p- in medicine.
The p-elements of the periodic table include elements with a valence p-sublevel. These elements are located in III, IV, V, VI, VII, VIII groups, main subgroups. During the period, the orbital radii of atoms decrease with increasing atomic number, but generally increase. In subgroups of elements, as the element number increases, the sizes of atoms generally increase and decrease. p-elements of group III Group III p-elements include gallium Ga, indium In and thallium Tl. By the nature of these elements, boron is a typical non-metal, the rest are metals. Within the subgroup there is a sharp transition from non-metals to metals. The properties and behavior of boron are similar, which is the result of the diagonal affinity of elements in the periodic table, according to which a shift in a period to the right causes an increase in non-metallic character, and down the group - a metallic character, therefore elements with similar properties are located diagonally next to each other, for example Li and Mg, Ber and Al, B and Si.
The electronic structure of the valence sublevels of atoms of group III p-elements in the ground state has the form ns 2 np 1 . In compounds, boron and trivalent, gallium and indium, in addition, can form compounds with +1, and for thallium the latter is quite characteristic.
p-elements of group VIII Group VIII p-elements include helium He, neon Ne, argon Ar, krypton Kr, xenon Xe and radon Rh, which form the main subgroup. The atoms of these elements have complete outer electronic layers, so the electronic configuration of the valence sublevels of their atoms in the ground state is 1s 2 (He) and ns 2 np 6 (other elements). Due to the very high stability of electronic configurations, they are generally characterized by high ionization energies and chemical inertness, which is why they are called noble (inert) gases. In a free state, they exist in the form of atoms (monatomic molecules). The atoms of helium (1s 2), neon (2s 2 2p 6) and argon (3s 2 3p 6) have a particularly stable electronic structure, so valence-type compounds are unknown for them.
Krypton (4s 2 4p 6), xenon (5s 2 5p 6) and radon (6s 2 6p 6) differ from the previous noble gases in their larger atomic sizes and, accordingly, lower ionization energies. They are capable of forming compounds that often have low stability.
The belonging of an element to the electronic family is determined by the nature of the filling of energy sublevels:
s-elements – filling the outer s-sublevel in the presence of two or eight electrons in the pre-external level, for example:
Li 1s 2 2s 2
s-elements are active metals, the characteristic oxidation states of which are numerically equal to the number of electrons at the last level:
1 for alkali metals and +2 for elements of the second group
p-elements – filling the outer p-sublevel, for example:
F 1s 2 2s 2 2p5
Elements B to Ne inclusive form the first series p-elements (elements of the main subgroups), in the atoms of which the electrons farthest from the nucleus are located on the second sublevel of the external energy level.
d-elements – filling of the pre-external d-sublevel, for example:
V 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 3
d-elements belong to metals.
f-elements – filling the f-sublevel of the second level outside, for example:
Nd 1s 2 2s 2 2p 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 4
f-elements are elements of the actinide and lanthanide families.
Quantum mechanics, comparing the electronic configurations of atoms, comes to the following theoretical conclusions:
1. The structure of the outer shell of an atom is a periodic function of the charge number of the atom Z.
2. Since the chemical properties of an atom are determined by the structure of the outer shell, it follows from the previous paragraph: the chemical properties of elements periodically depend on the charge of the nucleus.
Control questions
1. Nuclear model of the structure of the atom. Isotopes (radionuclides).
2. Quantum - mechanical model of the structure of the atom.
3. Quantum numbers (principal, orbital, magnetic, spin).
4. The structure of the electronic shells of atoms. Pauli's principle. Principle of least energy. Hund's rule.
5. Electronic structural formulas of atoms. Hybridization of atomic orbitals.
6. Characteristics of the atom. Atomic radius. Electronegativity. Electron affinity. Ionization energy. S, p, d, f – electron families of atoms.
Typical tasks
Problem No. 1. The radii of Na + and Cu + ions are the same (0.098 nm). Explain the difference in the melting points of sodium chloride (801°C) and copper(I) chloride (430°C).
With the same charges and sizes of the Na + and Cu + ions, the Cu + ion has an 18-electron outer shell and more strongly polarizes the Cl - anion than the Na + ion, which has the electronic structure of a noble gas. Therefore, in copper(I) chloride, as a result of polarization, a larger portion of the electronic charge is transferred from the anion to the cation than in sodium chloride. The effective charges of ions in a CuCl crystal become smaller than NaCl, and the electrostatic interaction between them becomes weaker. This explains the lower melting point of CuCl compared to NaCl, whose crystal lattice is close to the purely ionic type.
Task No. 2. How is the state of an electron indicated: a) with n=4,L=2; b) with n=5,L=3.
Solution: When writing an energy state, the number of the level (n) is indicated with a number, and the nature of the sublevel (s, p, d, f) is indicated with a letter. For n=4 and L=2 we write 4d; for n=5 and L=3 we write 5f.
Problem No. 3. How many orbitals in total correspond to the third energy level? How many electrons are there in this level? How many sublevels does this level split into?
Solution: For the third energy level n=3, the number of atomic orbitals is 9(3 2), which
is the sum of 1(s) +3(p) +5(d)=9. According to the Pauli principle, the number of electrons at this level is 18. The third energy level is split into three sublevels: s, p, d (the number of sublevels coincides with the number of values of the main quantum number).
Task No. 4. What electronic families are chemical elements classified into?
Solution: All chemical elements can be classified into 4 types depending on the nature of the sublevels being filled:
s-elements fill the ns sublevel with electrons;
p-elements - fill the np sublevel with electrons;
d-elements - fill the (n-1)d sublevel with electrons;
f-elements – fill the (n-2)f sublevel with electrons;
Problem No. 5. Which sublevel is filled in the atom with electrons after filling the sublevel: a) 4p; b)4s
Solution: A) sublevel 4p corresponds to the sum (n+1) equal to 4+1=5. The same sum characterizes sublevels 3d (3+2=5) and 5s (5+0=5). However, state 3d corresponds to a smaller value of n (n=3) than state 4p, so sublevel 3d will be filled earlier than sublevel 4p. Consequently, after filling the 4p sublevel, the 5s sublevel will be filled, which corresponds to a greater value of n(n=5) by one.
B) sublevel 4s corresponds to the sum n+1=4+0=4. The same sum n+1 characterizes the 3p sublevel, but the filling of this sublevel precedes the filling of the 4s sublevel, because the latter corresponds to a larger value of the principal quantum number. Consequently, after sublevel 4s, a sublevel with the sum (n+1)=5 will be filled, and out of all possible combinations n+l corresponding to this sum (n=3, l=2; n=4; l=1; n=5 ; l=0), the combination with the smallest value of the main quantum number will be realized first, that is, after the 4s sublevel, the 3d sublevel will be filled.
Conclusion: thus, the filling of the d sublevel lags behind by one quantum level, the filling of the f sublevel lags behind by two quantum levels.
To write the electronic formula of an element, you must: indicate the energy level number in Arabic numerals, write the letter value of the sublevel, and write the number of electrons as an exponent.
For example: 26 Fe 4 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6
The electronic formula is compiled taking into account the competition of sublevels, i.e. minimum energy rules. Without taking the latter into account, the electronic formula will be written: 26 Fe 4 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2.
Problem No. 6. The electronic structure of an atom is described by the formula 1s22s22p63s23d74s2. What element is this?
Solution: This element belongs to the electronic type of d-elements of the 4th period, because the 3d sublevel is built up by electrons; the number of electrons 3d 7 indicates that it is the seventh element in order. The total number of electrons is 27, which means the atomic number is 27. This element is cobalt.
Test tasks
Choose the correct answer
01. THE ELECTRONIC FORMULA OF THE ELEMENT IS ... 5S 2 4D 4. INDICATING THE NUMBER OF ELECTRONS IN THE OUTER LEVEL
02. CAN TWO ELECTRONS WITH THE SAME SET OF ALL FOUR QUANTUM NUMBERS EXIST IN AN ATOM?
1) can't
They can
3) can only in an excited state
4) can only in a normal (unexcited) state
03. WHICH SUB-LEVEL IS FILLED AFTER SUB-LEVEL 4D?
04. THE ELECTRONIC FORMULA OF THE ELEMENT IS: 1S 2 2S 2 2P 6 3S 2. SPECIFY THE NUMBER OF VALENCE ELECTRONS
05. THE ELECTRONIC FORMULA OF THE ELEMENT IS: 1S 2 2S 2 2P 6 3S 2 3P 6 4S 2 3D 7. WHAT ELEMENT IS THIS?
06. WHICH SUB-LEVEL IS FILLED BEFORE THE 4D SUB-LEVEL?
07. AMONG THE ELECTRONIC CONFIGURATIONS LISTED BELOW, SPECIFY THE IMPOSSIBLE
08. THE ELECTRONIC STRUCTURE OF AN ATOM OF AN ELEMENT IS EXPRESSED BY THE FORMULA: 5S 2 4D 3. DETERMINE WHAT ELEMENT IT IS.
Elements in Mendeleev's periodic table are divided into s-, p-, d-elements. This division is carried out on the basis of how many levels the electron shell of an element’s atom has and at what level the filling of the shell with electrons ends.
TO s-elements include elements IA-groups – alkali metals. Electronic formula of the valence shell of alkali metal atoms ns1. The stable oxidation state is +1. Elements IA-groups have similar properties due to the similar structure of the electron shell. As the radius in the Li-Fr group increases, the bond between the valence electron and the nucleus weakens and the ionization energy decreases. Atoms of alkaline elements easily give up their valence electron, which characterizes them as strong reducing agents.
The reducing properties increase with increasing serial number.
TO p-elements include 30 elements IIIA-VIIIA-groups periodic table; p-elements are located in the second and third minor periods, as well as in the fourth to sixth major periods. Elements IIIA-groups have one electron in the p orbital. IN IVA-VIIIA-groups the filling of the p-sublevel with up to 6 electrons is observed. General electronic formula of p-elements ns2np6. In periods with increasing nuclear charge, the atomic radii and ionic radii of p-elements decrease, ionization energy and electron affinity increase, electronegativity increases, the oxidative activity of compounds and the non-metallic properties of elements increase. In groups, the radii of atoms increase. From 2p elements to 6p elements, the ionization energy decreases. The metallic properties of the p-element in the group increase with increasing atomic number.
TO d-elements There are 32 elements of the periodic table IV–VII major periods. IN IIIB-group atoms have the first electron in the d-orbital, in subsequent B-groups the d-sublevel is filled with up to 10 electrons. General formula for the outer electron shell (n-1)dansb, where a=1?10, b=1?2. With an increase in the ordinal number, the properties of d-elements change slightly. The d-elements slowly increase in atomic radius, and they also have a variable valency associated with the incompleteness of the outer d-electron sublevel. In lower oxidation states, d-elements exhibit metallic properties; with an increase in the atomic number in groups B, they decrease. In solutions, d-elements with the highest oxidation state exhibit acidic and oxidizing properties, and vice versa at lower oxidation states. Elements with intermediate oxidation states exhibit amphoteric properties.
8. Covalent bond. Valence bond method
A chemical bond carried out by common electron pairs arising in the shells of bonded atoms having antiparallel spins is called atomic or covalent bond. The covalent bond is two-electron and two-center (holds the nuclei). It is formed by atoms of one type - covalent non-polar– a new electron pair, arising from two unpaired electrons, becomes common to two chlorine atoms; and atoms of different types, similar in chemical character - covalent polar. Elements with greater electronegativity (Cl) will withdraw shared electrons from elements with less electronegativity (H). Atoms with unpaired electrons having parallel spins repel each other - no chemical bond occurs. The method of forming a covalent bond is called exchange mechanism.
Properties of covalent bonds. Link length – internuclear distance. The shorter this distance, the stronger the chemical bond. Communication energy – the amount of energy required to break a bond. The bond multiplicity is directly proportional to the bond energy and inversely proportional to the bond length. Communication direction – a specific arrangement of electron clouds in a molecule. Saturability– the ability of an atom to form a certain number of covalent bonds. A chemical bond formed by overlapping electron clouds along an axis connecting the centers of atoms is called ?-connection. A bond formed by overlapping electron clouds perpendicular to the axis connecting the centers of atoms is called ?-connection. The spatial orientation of a covalent bond is characterized by the angles between the bonds. These angles are called bond angles. Hybridization – the process of restructuring electron clouds of unequal shape and energy, leading to the formation of hybrid clouds identical in the same parameters. Valence– number of chemical bonds (covalent ), through which an atom is connected to others. Electrons involved in the formation of chemical bonds are called valence. The number of bonds between atoms is equal to the number of its unpaired electrons participating in the formation of common electron pairs, therefore valence does not take into account polarity and has no sign. In compounds in which there is no covalent bond, there is oxidation state – the conventional charge of an atom, based on the assumption that it consists of positively or negatively charged ions. The concept of oxidation state applies to most inorganic compounds.
