Question

What are shells? Write the maximum number of electrons that they can accommodate.

Answer 1

• Neils Bohr proposed that every atom consists of a small heavy positively charged nucleus in its centre. The electrons are revolving around the nucleus in the definite circular path known as orbits or shells.
• Every orbit or shell is associated with a definite amount of energy. Hence orbits are also called energy shells.
• The energy shells are represented by the letters K, L, M, and N or numbers 1,2,3,4.
• K-shell(n=1) is near to the nucleus, L shell (n=2) is the second shell, M-shell (n=3) is the 3rd shell, and so on.
• The energy of these shells increases as we move outwards from the nucleus.
• Electrons accommodated in a particular shell is given by the formulae $2{\mathrm{n}}^2$, where $\mathrm{n}$is the number of the orbit.

Shell	Value of n	Maximum number of electron
K	1	$2*1^2=2$
L	2	$2*2^2=2*4=8$
M	3	$2*3^2=2*9=18$
N	4	$2*4^2=2*16=32$