Question

Explain the arrangement of electrons in an atom by giving examples.

Answer 1

Arrangement of electrons:

1. Electrons are negatively charged particles that revolve around the nucleus.
2. The electrons form a cloud of negative charge which revolve around the nucleus in definite orbits called shells.
3. The shells are also called energy levels.
4. The shell closest to the nucleus is called $\mathrm{K}$ shell, the first shell.
5. The next shell is called the $\mathrm{L}$ shell.
6. The shells next to the $\mathrm{L}$ shell are $\mathrm{M}$ shell and $\mathrm{N}$ shell.
7. According to the Bohr-Bury scheme, the electrons are distributed in shells.

Shell	Shell number	$2{\mathrm{n}}^2$	Maximum number of electrons in each shell
$\mathrm{K}$	$1$	${2\times \left(1\right)}^2$	$2$ electrons
$\mathrm{L}$	$2$	${2\times \left(2\right)}^2$	$8$ electrons
$\mathrm{M}$	$3$	${2\times \left(3\right)}^2$	$18$electrons
$\mathrm{N}$	$4$	${2\times \left(4\right)}^2$	$32$electrons

Examples:

1. Helium atom:

• Helium consists of 2 electrons.
• The 2 electrons are arranged in $\mathrm{K}$ shell.

2. Carbon atom:

• Carbon consists of 6 electrons, i.e 2.
• The 2 electrons are present in $\mathrm{K}$ shell, and 4 electrons are present in $\mathrm{L}$ shell, i.e. 2,6.