Atomic structure. Theories about atomic structure. DIMendeleev periodic law of elements. Modern tariff of periodic law.
Plan:
1. Atomic structure. The component of an atom (nucleus, protons, neutrons).
2. Atomic orbitals. Characterizing the energies of electrons with quantum numbers.
3. Distribution of electrons along orbitals in multi-electron atoms. Pauli principle. Diet rule.
4. The maximum number of electrons that can be in the energy levels.
5. Mendeleyev's periodic law of elements and its role and importance in the development of inorganic chemistry.
6. Modern definition of periodic law.
At the end of the 25th century, 19 elements were known, and in the first quarter of the XNUMXth century, XNUMX more elements were discovered. As a result of the discovery of new elements, the existence of natural groups of some elements was noticed. For example, alkali metals, alkaline-earth metals, halogens are among them.
The study of elements and their combinations required the classification of existing substances into different classifications.
Many attempts have been made to combine elements in the form of specific groups based on the similarity of their properties. But scientists could not come to a clear solution in finding the internal connections between the groups and uniting the elements into a single system.
DiMendeleev (1834-1907) successfully solved the problem of systematizing chemical elements. He discovered the periodic law in 1869 and created the periodic table of chemical elements. Mendeleev used atomic mass as a basis for systematizing elements. He placed the chemical elements in order of increasing atomic mass and determined that elements-analogs with similar properties meet at a fixed interval, that is, after a certain number of elements. Therefore, certain properties of elements are repeated periodically. In other words, the properties of elements are periodic functions of their atomic masses.
This regularity in the change of the properties of the elements is expressed in the periodic law. The properties of simple substances, as well as the form and properties of the combinations of elements, periodically depend on the size of the atomic masses of the elements.
The elements are arranged in a certain sequence, in which their properties change in a certain regularity from the obvious metallic property to the non-metallic property. Mendeleev called the period during which such changes in the properties of elements occur. Placing all the periods under each other, Mendeleev creates a table called the periodic system of elements. In some cases, Mendeleev violated the principle of arrangement of elements in the order of increasing atomic mass by placing an element with a small atomic mass after an element with a large atomic mass (tellurium and iodine: Te, J).
Because when creating the periodic system, Mendeleev was not only based on the atomic mass of the elements, but also considered all their physical and chemical properties. In addition, he determined the atomic masses of several elements: Ve, Jn, U, Th (beryllium, indium, uranium, thorium).
One of the main difficulties faced by Mendeleev in creating the periodic table was that many elements were not known at that time: he left room for one more element (Sc) between Sa and Ti.
Such places are left between Zn, As (zinc and arsenic), Mo, Ru (molybdenum and ruthenium) in the periodic table. Based on the periodic law, Mendeleev boldly stated that there are several elements in nature that have not yet been identified. These elements are 21 (Sc), 31 (Ga), 32 (Ge) in the current table.
An atom is a complex system consisting of a positively charged nucleus and negatively charged electrons moving around the nucleus. The atomic nucleus is made up of protons and neutrons. A proton has a mass of about 1 carbon unit and a charge of +1. A neutron is an uncharged particle with a mass approximately equal to the mass of a proton. Proton is conventionally denoted by: 1p, and neutron by 1n. Electrons, like any other elementary particles, have mass and exhibit wave properties. An electron has a wavelength of 9,1*10-27g and a charge of 1*1010 cm.
Since the electron particle has a wave nature, it moves around the atomic nucleus forming several quantum layers. These quantum layers are called energy layers.
The movement of electrons is represented by 4 quantum numbers. The principal quantum number - n indicates how many energy poles are around the atomic nucleus, and its numerical value is equal to the sequence number of a particular period in the periodic system.
The values of n are denoted by the letters 1, 2, 3, 4, 5, 6, 7 … or K, L, M, N, O, P …. The maximum value of electrons in any energy level is expressed by the following formula.
N = 2n2 n is the prime quantum number
The shape of the electron poKona (orbit) is characterized by the orbital or lateral quantum number - L.
Values of L are usually specified as integers or lowercase Latin letters.
L = 0, 1, 2, 3, 4, 5...
L = s, p, d, f, q, h
The position of electron orbits in space is characterized by magnetic quantum number (m). m - shows how many different orbits there are in the same energetic poKona and the position of these orbits in space.
The fourth quantum number is called the spin quantum number and is denoted by ms. Its numerical values can be +1/ 2 and -1/ 2.
According to the Pauli principle, an atom cannot have two electrons with equal four quantum numbers. Each electron tends to occupy the state corresponding to the lowest energy.
The procedure for filling energy cells and cells with electrons is expressed as follows:
1s<2s<2p<3s<3p<4s<3d<4p<5s<4d<5p<6s<4f<5d<6p<7s
All elements in the periodic system (с, п, д, ф) are divided into electron families, depending on the location of the last electron in the s-, p-, d- and f-levels in the energy levels of atoms.
1 is an example. Draw the electronic formula of an atom of element with atomic number 17.
Solution: In the periodic table, element number 17 is chlorine, which is located in the main group of the seventh group of the third period. Its electronic formula is as follows:
1s22s22p63s23p5
So CL r is an element.
2 is an example. How are electrons distributed in energy levels and sublevels in Mn atom with atomic number 25. What electron family does this element belong to?
Solution: The 25 electrons in an atom of an element are distributed as follows:
1s22s22p63s23p63d54s2
This element belongs to the d-family because the most recent electron is in the d poColon.
DIMendeleyev in 1869 discovered the periodic law of chemical elements, the law of nature. In the periodic table, the properties of elements are characterized by their sequence number (nuclear charge).
The periodic table is defined as:
"The properties of simple substances (elements), as well as the forms and properties of element compounds, are periodically dependent on the size of the nuclear charge of the elements."
In the periodic system, all elements are placed in 7 periods: periods 1, 2, 3 are small periods 4, 5, 6 are large periods. 7 is an incomplete period. The periodic table consists of 8 groups. Each group consists of a main group (A) and an additional group (V).
Books:
1. Rakhimov XR Inorganic chemistry. II edition. T. "teacher". 1984.
2. Akhmerov KM, Jalilov A., Ismailov A. General and inorganic chemistry. T. "teacher. 1988.
3. Akhmetov NS Inorganic chemistry. Visshaya school. 1975.
