ENERGY LEVELS
| Parameter name | Meaning |
| Article topic: | ENERGY LEVELS |
| Rubric (thematic category) | Education |
ATOMIC STRUCTURE
1. Development of the theory of atomic structure. WITH
2. The nucleus and electron shell of the atom. WITH
3. Structure of the nucleus of an atom. WITH
4. Nuclides, isotopes, mass number. WITH
5. Energy levels.
6. Quantum mechanical explanation of the structure.
6.1. Orbital model of the atom.
6.2. Rules for filling orbitals.
6.3. Orbitals with s-electrons (atomic s-orbitals).
6.4. Orbitals with p-electrons (atomic p-orbitals).
6.5. Orbitals with d-f electrons
7. Energy sublevels of a multielectron atom. Quantum numbers.
ENERGY LEVELS
The structure of the electron shell of an atom is determined by the different energy reserves of individual electrons in the atom. In accordance with the Bohr model of the atom, electrons can occupy positions in the atom that correspond to precisely defined (quantized) energy states. These states are called energy levels.
The number of electrons that can be in a separate energy level is determined by the formula 2n 2, where n is the number of the level, which is denoted by Arabic numerals 1 - 7. The maximum filling of the first four energy levels is c. according to the formula 2n 2 is: for the first level – 2 electrons, for the second – 8, for the third – 18 and for the fourth level – 32 electrons. The maximum filling of higher energy levels with electrons in the atoms of known elements has not been achieved.
Rice. 1 shows the filling of the energy levels of the first twenty elements with electrons (from hydrogen H to calcium Ca, black circles). By filling the energy levels in the indicated order, we obtain the simplest models of atoms of elements, while observing the order of filling (from bottom to top and from left to right in the figure) until the last electron points to the symbol of the corresponding element. On the third energy level M(maximum capacity is 18 e -) for the elements Na – Ar there are only 8 electrons, then the fourth energy level begins to be built up N– two electrons appear on it for the elements K and Ca. The next 10 electrons again occupy the level M(elements Sc – Zn (not shown), and then the N level continues to be filled with six more electrons (elements Ca-Kr, white circles).
| Rice. 1 | Rice. 2 |
If the atom is in the ground state, then its electrons occupy levels with minimal energy, i.e., each subsequent electron occupies the most energetically favorable position, such as in Fig. 1. Under external influence on an atom associated with the transfer of energy to it, for example by heating, electrons are transferred to higher energy levels (Fig. 2). This state of the atom is usually called excited. The space vacated at the lower energy level is filled (as an advantageous position) by an electron from a higher energy level. During the transition, the electron gives up a small amount of energy, which corresponds to the energy difference between the levels. As a result of electronic transitions, characteristic radiation appears. From the spectral lines of absorbed (emitted) light, a quantitative conclusion can be made about the energy levels of the atom.
In accordance with Bohr's quantum model of the atom, an electron having a certain energy state moves in a circular orbit in the atom. Electrons with the same amount of energy are located at equal distances from the nucleus; each energy level has its own set of electrons, which Bohr called the electron layer. However, according to Bohr, the electrons of one layer move along a spherical surface, the electrons of the next layer move along another spherical surface. all spheres are inscribed one into another with a center corresponding to the atomic nucleus.
ENERGY LEVELS - concept and types. Classification and features of the category "ENERGY LEVELS" 2017, 2018.
Today we will talk about what the energy level of an atom is, when a person encounters this concept, and where it is applied.
School physics
People first encounter natural sciences in school. And if in the seventh year of study children still find new knowledge in biology and chemistry interesting, then in high school they begin to be afraid of them. When the turn of atomic physics comes, lessons in this discipline already inspire only disgust for incomprehensible tasks. However, it is worth remembering that all discoveries that have now turned into boring school subjects have a non-trivial history and a whole arsenal of useful applications. Finding out how the world works is like opening a box with something interesting inside: you always want to find the secret compartment and discover another treasure there. Today we will talk about one of the basic physics, the structure of matter.
Indivisible, composite, quantum
From the ancient Greek language the word “atom” is translated as “indivisible, smallest.” This idea is a consequence of the history of science. Some ancient Greeks and Indians believed that everything in the world was made up of tiny particles.
In modern history, physical research was carried out much earlier. Scholars of the seventeenth and eighteenth centuries worked primarily to increase the military power of the country, king, or duke. And in order to create explosives and gunpowder, it was necessary to understand what they consist of. As a result, the researchers found that some elements cannot be separated beyond a certain level. This means that there are the smallest carriers of chemical properties.
But they were wrong. The atom turned out to be a composite particle, and its ability to change is quantum in nature. This is also evidenced by transitions in the energy levels of the atom.
Positive and negative
At the end of the nineteenth century, scientists came close to studying the smallest particles of matter. For example, it was clear: an atom contains both positively and negatively charged components. But it was unknown: the location, interaction, and weight ratio of its elements remained a mystery.
Rutherford conducted an experiment on the scattering of thin alpha particles. He found out that in the center of the atoms there are heavy positive elements, and very light negative ones are located at the edges. This means that the carriers of different charges are particles that are not similar to each other. This explained the charge of atoms: an element could be added to them or one could be removed. The equilibrium that maintained the neutrality of the entire system was disrupted, and the atom acquired a charge.
Electrons, protons, neutrons
Later it turned out that light negative particles are electrons, and a heavy positive nucleus consists of two types of nucleons (protons and neutrons). Protons differed from neutrons only in that the former were positively charged and heavy, while the latter only had mass. Changing the composition and charge of the nucleus is difficult: it requires incredible amounts of energy. But an atom is divided much more easily by an electron. There are more electronegative atoms that are more willing to “take away” an electron, and less electronegative atoms that are more likely to “give” it up. This is how the charge of an atom is formed: if there is an excess of electrons, then it is negative, and if there is a deficiency, then it is positive.
Long life of the universe
But this atomic structure puzzled scientists. According to the prevailing classical physics of those times, an electron, which was constantly moving around the nucleus, should have continuously emitted electromagnetic waves. Since this process means a loss of energy, all negative particles would soon lose their speed and fall onto the core. However, the universe has existed for a very long time, and a worldwide catastrophe has not yet occurred. The paradox of matter being too old was brewing.
Bohr's postulates
Bohr's postulates were able to explain the discrepancy. Then these were simply statements, leaps into the unknown, which were not supported by calculations or theory. According to the postulates, there were energy levels of electrons in the atom. Each negatively charged particle could only be at these levels. The transition between orbitals (as the levels are called) is carried out by a jump, in which a quantum of electromagnetic energy is released or absorbed.
Planck's discovery of the quantum later explained this behavior of electrons.
Light and atom
The amount of energy required for the transition depends on the distance between the energy levels of the atom. The farther they are from each other, the greater the emitted or absorbed quantum.
As you know, light is a quantum of the electromagnetic field. Thus, when an electron in an atom moves from a higher to a lower level, it creates light. In this case, the opposite law also applies: when an electromagnetic wave falls on an object, it excites its electrons, and they move to a higher orbital.
In addition, the energy levels of an atom are individual for each type of chemical element. The pattern of distances between orbitals differs for hydrogen and gold, tungsten and copper, bromine and sulfur. Therefore, analysis of the emission spectra of any object (including stars) unambiguously determines what substances are present in it and in what quantities.
This method is used incredibly widely. Spectral analysis is used:
- in criminology;
- in food and water quality control;
- in the production of goods;
- in the creation of new materials;
- in improving technology;
- in scientific experiments;
- in the study of stars.
This list only roughly shows how useful the discovery of electronic levels in the atom turned out to be. Electronic levels are the roughest, the largest. There are finer vibrational and even finer rotational levels. But they are relevant only for complex compounds - molecules and solids.
It must be said that the structure of the nucleus has not yet been fully studied. For example, there is no answer to the question of why a certain number of protons corresponds to exactly that number of neutrons. Scientists suggest that the atomic nucleus also contains some analogue of electronic levels. However, this has not yet been proven.
Answer from Ksenia Gareeva[guru]
period number
Answer from Slava mikailov[newbie]
Answer from Bet[guru]
Energy level
Material from Wikipedia - the free encyclopedia
Energy level - possible energy values of quantum systems, i.e. systems consisting of microparticles (electrons, protons and other elementary particles, atomic nuclei, atoms, molecules, etc.) and subject to the laws of quantum mechanics. Characterizes a certain state of the microparticle. There are electronic and intranuclear energy levels.
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Electronic energy levels
The modern concept of the orbital model of an atom, in which electrons move from one energy level to another, and the difference between the energy levels determines the size of the emitted or absorbed quantum. In this case, electrons cannot be located in the gaps between energy levels. These gaps are called the forbidden energy zone.
An example is an electron in the orbital model of an atom - depending on the values of the principal quantum number n and the orbital quantum number l, the energy level possessed by the electron changes. Accordingly, each pair of values of numbers n and l corresponds to a certain energy level.
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Intranuclear energy levels
The term originated from research into radioactivity. Radiation is divided into three parts: alpha rays, beta rays and gamma rays. Research has shown that alpha radiation consisted of helium atoms, beta radiation is a stream of fast-moving electrons, and research on gamma rays has shown that the energy of electronic levels is not enough to produce them. It became clear that the source of radioactive radiation (gamma rays) must be sought inside the atomic nucleus, that is, there are intranuclear energy levels, the energy of which is converted into photons of gamma radiation. Gamma rays have expanded the spectrum of known electromagnetic waves, and all waves shorter than 0.01 nm are gamma rays.
A. 2e, 8e, 8e, 1e B. . 2e, 8e,
18th, 8th, 1st
B. 2e, 1e D. 2e, 8e, 1e
2 (2 points). The number of electrons in the outer electron layer of an aluminum atom:
A. 1 B. 2 C. 3 D.4
3 (2 points). A simple substance with the most pronounced metallic properties:
A. Calcium B. Barium C. Strontium D. Radium
4 (2 points). Type of chemical bond in a simple substance - aluminum:
A. Ionic B. Covalent polar
B. Metallic D. Covalent nonpolar
5 (2 points). The number of energy levels of elements of one subgroup from top to bottom:
A. Changes periodically. B. Does not change.
B. Increases. D. Decreases.
6 (2 points). A lithium atom differs from a lithium ion:
A. 3-near the nucleus. B. The number of electrons at the external energy level.
B. The number of protons. D. The number of neutrons.
7 (2 points). Reacts least vigorously with water:
A. Barium. B. Magnesium.
B. Calcium. G. Strontium
8 (2 points). Does not interact with sulfuric acid solution:
A. Aluminum. B. Sodium
B. Magnesium. G. Copper
9 (2 points). Potassium hydroxide does not react with a substance whose formula is:
A. Na2O B. AlCl3
B. P2O5 D. Zn(NO3)2
10 (2 points). A series in which all substances react with iron:
A. HCl, CO2, CO
B. CO2, HCl, S
B. H2, O2, CaO
G. O2, CuSO4, H2SO4
11 (9 points). Suggest three ways to obtain sodium hydroxide. Confirm your answer with reaction equations.
12 (6 points). Carry out a chain of chemical transformations by drawing up reaction equations in molecular and ionic forms, name the reaction products:
FeCl2 → Fe(OH)2 → FeSO4 → Fe(OH)2
13 (6 points). How, using any reagents (substances) and zinc, to obtain its oxide, base, salt? Write down reaction equations in molecular form.
14 (4 points). Write an equation for the chemical reaction between lithium and nitrogen. Identify the reducing agent and oxidizing agent in this reaction
determine by:
A. group number;
B. period number;
B. serial number.
4. Which of the characteristics of chemical elements does not change in the main subgroups:
And the radius of the atom;
B the number of electrons in the outer level;
B. number of energy levels.
5. The structure of the atoms of elements with serial numbers 7 and 15 has something in common:
A. number of electrons in the outer level, B. charge of the nucleus;
B. number of energy levels.
Establish a correspondence between the symbol of a chemical element (in a given order) and the number of electrons in the outer energy level of its atom. From lettersBased on the correct answers, you will create the name of an installation that will allow humanity to understand the structure of the atom even more deeply (9 letters).
Number e on Element Symbol
Energy
level Mg Si I F C Ba Sn Ca Br
2 drops of sem
4 a o v k a t d h i
7 v y l l n g o l r
1 (3 points). Distribution of electrons by energy levels in the sodium atom -A. 2 ē, 1 ē B. 2 ē, 4 ē C. 2 ē, 8 ē, 1 ē. G. 2 ē, 8 ē, 3 ē.
2 (4 points) Number of the period in the Periodic Table of D. I. Mendeleev, in which there are no chemical elements-metals: A. 1. B. 2. C. 3. D. 4.
3 (3 points). Type of chemical bond in the simple substance calcium:
A. Ionic. B. Covalent polar. B. Covalent nonpolar. G. Metal.
4 (3 points). A simple substance with the most pronounced metallic properties:
A. Aluminum. B. Silicon. B. Magnesium. G. Sodium.
5 (3 points). The radius of atoms of elements of the 2nd period with increasing nuclear charge from an alkali metal to a halogen: A. Changes periodically. B. Does not change. B. Increases. D. Decreases.
6 (3 points). A magnesium atom differs from a magnesium ion:
A. Nuclear charge. B. Charge of the particle. B. The number of protons. D. The number of neutrons.
7 (3 points). Reacts most vigorously with water:
A. Potassium. B. Lithium. B. Sodium. G. Rubidium.
8 (3 points). Does not react with dilute sulfuric acid:
A. Aluminum. B. Barium. B. Iron. G. Mercury.
9 (3 points). Beryllium hydroxide does not interact with a substance whose formula is:
A. NaOH(p p). B. NaCl(p_p). B. NS1(r_r). G. H2SO4.
10 (3 points). A series in which all substances react with calcium:
A. CO2, H2, HC1. B. NaOH, H2O, HC1. B. C12, H2O, H2SO4. G. S, H2SO4, SO3.
PART B. Free-response questions
11 (9 points). Suggest three ways to obtain iron (II) sulfate. Confirm your answer with reaction equations.
12 (6 points). Identify substances X, Y, Z, write down their chemical formulas.
Fe(OH)3(t)= X(+HCl)= Y(+NaOH)=Z(t) Fe2O3
13 (6 points). How, using any reagents (substances) and aluminum, to obtain an oxide, amphoteric hydroxide? Write down reaction equations in molecular form.
14 (4 points). Arrange the metals: copper, gold, aluminum, lead in order of increasing density.
15 (5 points). Calculate the mass of the metal obtained from 160 g of copper (II) oxide.
What happens to the atoms of elements during chemical reactions? What do the properties of elements depend on? One answer can be given to both of these questions: the reason lies in the structure of the external level. In our article we will look at the electronics of metals and non-metals and find out the relationship between the structure of the external level and the properties of the elements.
Special properties of electrons
When a chemical reaction occurs between the molecules of two or more reagents, changes occur in the structure of the electronic shells of atoms, while their nuclei remain unchanged. First, let's get acquainted with the characteristics of electrons located at the levels of the atom farthest from the nucleus. Negatively charged particles are arranged in layers at a certain distance from the nucleus and from each other. The space around the nucleus where electrons are most likely to be found is called an electron orbital. About 90% of the negatively charged electron cloud is condensed in it. The electron itself in an atom exhibits the property of duality; it can simultaneously behave both as a particle and as a wave.
Rules for filling the electron shell of an atom
The number of energy levels at which the particles are located is equal to the number of the period where the element is located. What does the electronic composition indicate? It turned out that at the external energy level for s- and p-elements the main subgroups of small and large periods correspond to the group number. For example, lithium atoms of the first group, which have two layers, have one electron in the outer shell. Sulfur atoms contain six electrons at the last energy level, since the element is located in the main subgroup of the sixth group, etc. If we are talking about d-elements, then for them there is the following rule: the number of external negative particles is equal to 1 (for chromium and copper) or 2. This is explained by the fact that as the charge of the atomic nucleus increases, the internal d-sublevel is first filled and the external energy levels remain unchanged.
Why do the properties of elements of small periods change?
The 1st, 2nd, 3rd and 7th periods are considered small. The smooth change in the properties of elements as nuclear charges increase, from active metals to inert gases, is explained by a gradual increase in the number of electrons at the external level. The first elements in such periods are those whose atoms have only one or two electrons that can easily be stripped from the nucleus. In this case, a positively charged metal ion is formed.
Amphoteric elements, for example, aluminum or zinc, fill their outer energy levels with a small number of electrons (1 for zinc, 3 for aluminum). Depending on the conditions of the chemical reaction, they can exhibit both the properties of metals and non-metals. Non-metallic elements of small periods contain from 4 to 7 negative particles on the outer shells of their atoms and complete it to the octet, attracting electrons from other atoms. For example, the nonmetal with the highest electronegativity, fluorine, has 7 electrons in the last layer and always takes one electron not only from metals, but also from active nonmetallic elements: oxygen, chlorine, nitrogen. Small periods, like large ones, end with inert gases, whose monatomic molecules have completely completed outer energy levels up to 8 electrons.
Features of the structure of atoms of long periods
The even rows of periods 4, 5, and 6 consist of elements whose outer shells accommodate only one or two electrons. As we said earlier, they fill the d- or f-sublevels of the penultimate layer with electrons. Usually these are typical metals. Their physical and chemical properties change very slowly. Odd rows contain elements whose outer energy levels are filled with electrons according to the following scheme: metals - amphoteric element - nonmetals - inert gas. We have already observed its manifestation in all small periods. For example, in the odd row of the 4th period, copper is a metal, zinc is amphoteric, then from gallium to bromine there is an increase in non-metallic properties. The period ends with krypton, the atoms of which have a completely completed electron shell.
How to explain the division of elements into groups?
Each group - and there are eight of them in the short form of the table - is also divided into subgroups, called main and secondary. This classification reflects the different positions of electrons on the external energy level of atoms of elements. It turned out that for elements of the main subgroups, for example, lithium, sodium, potassium, rubidium and cesium, the last electron is located on the s-sublevel. Group 7 elements of the main subgroup (halogens) fill their p-sublevel with negative particles.
For representatives of side subgroups, such as chromium, filling the d-sublevel with electrons will be typical. And for elements included in the families, the accumulation of negative charges occurs at the f-sublevel of the penultimate energy level. Moreover, the group number, as a rule, coincides with the number of electrons capable of forming chemical bonds.
In our article, we found out what structure the external energy levels of atoms of chemical elements have, and determined their role in interatomic interactions.