# Electron Configuration Practice Worksheet

Electron configuration is the arrangement of electrons in an atom, molecule and other physical structures. Like other elementary particles, electrons follow the laws of quantum mechanics and display the properties of both particles and waves. Knowledge of the electron configuration of atoms is very useful in helping to understand the structure of the periodic table of the elements. This concept is also useful in explaining.

Table of Contents

## HISTORY OF ELECTRON CONFIGURATION

Initially, Neils Bohr proposed the Bohr model of the atom in which electron shells are in the form of orbits with fixed distances from the atomic nucleus. The original Bohr configuration was different from the one currently used: for example sulfur configured 2.4.4.6 instead of 1s2 2s2 2p2 etc.

Stu years later, E.C. Stoner included a third quantum number in the description of the electron shell and correctly predicted the structure of sulfur as 2.8.6. But neither Bohr nor Stoner could properly explain the changes in the atomic spectra and magnetic field.

Then, with the help of Wolfgang Pauli, who realized that the Zeeman effect was caused by the outer electrons of the atom. It can also reproduce the correct stonary shell structure by entering a fourth quantum number.

Another equation is that Schodinger generates three out of four quantum numbers as a consequence of solving for the Hydrogen atom. This solution yields atomic orbitals which we can find in chemistry textbooks. Atomic spectra studies can be determined experimentally which ultimately yields an empirical rule for which atomic orbital sequence is filled with electrons first.

## ELECTRON CONFIGURATION BASED ON ATOMIC SKIN

The electron configuration in each atomic shell can contain a maximum of 2n2 electrons, where n is the order of the atomic shells.

If n = 1 then 2n2 equals 2 electrons

If n = 2 then 2n2 equals 8 electrons

If n = 3 then 2n2 equals 18 electrons

If n = 4 then 2n2 equals 32 electrons

Each shell has a symbol where K equals the first shell close to the atomic nucleus, L after it, M after L, and N after M. The number of shells filled with electrons indicates the period. The electrons are arranged in such a way in each shell and are filled to the maximum according to the capacity of the shell. If there are still electrons left that can no longer be accommodated in the shell, then they are placed in the next shell.

## ELECTRON VALENCE

The electrons that play a role in the formation of chemical bonds and in chemical reactions are the outermost electrons or valence electrons. The number of valence electrons is determined based on the electrons contained in the last shell of the atom’s electron configuration. Elements that have the same number of valence electrons will have the same chemical properties.

## REGULATIONS FOR DETERMINING ELECTRON CONFIGURATION

In determining the configuration of an atom, we cannot easily do it without knowing the rules. There are 3 rules that must be taken into account, namely the aufbau principle, the pauli prohibition and the hund rule.

1. The Aufbau Principle

According to this principle, the electrons in the atom have the lowest energy possible. The filling of electrons in orbitals always starts from the 1s orbital or the lowest energy level. If the 1s orbital is full, the electrons will go into the 2s orbital, and so on.

The size of the orbital level depends on the value of the principal quantum number (n) and the azimuth quantum number (l). The orbital with the greater n + l value has a greater energy level. If the values ​​for n + l are the same, then the orbital that has a higher value for n has more energy.

The order of energy levels in electron charging is as follows.

## ELECTRONIC CHARGING

1. The Pauli ban

The principle of Paul’s prohibition states that it is impossible in an atom to have two electrons with the same four quantum numbers. That is, in an atom, two electrons may have the same values ​​for n, l, and ml, but their values ​​for s must be different. Thus, the pauli prohibition describes a maximum orbital to which only two electrons in opposite spin directions can occupy. The s subshell has 1 orbital, the maximum number of electrons is 2.

The p subshell has 3 orbitals and a maximum of 6 electrons

The p subshell has 5 orbitals and a maximum of 10 electrons

The p subshell has 7 orbitals and a maximum of 14 electrons

Maximum number of electrons in the –nth shell = 2n2.

1. The Hund Rule

In filling the orbitals with the same energy, the electrons will occupy the orbitals separately with parallel spins and then pair up. The lowest energy state is the one with the most unpaired electrons.