ATOMIC STRUCTURE

ATOMIC STRUCTURE

An atom consists of two parts :

Nucleus :

Nucleus is situated in the centre of an atom. All the protons & neutrons are situated in the nucleus, therefore, the entire mass of an atom is almost concentrated in the nucleus. The overall charge of nucleus is positive due to the presence of positively charged protons (neutrons present have no charge). The protons & neutrons are collectively called nucleons. The radius of the nucleus of an atom is of the order of 10-15 m.

Extra nuclear region:

In extra nuclear part or in the region outside the nucleus, electrons are present which revolve around the nucleus in orbits of fixed energies. These orbits are called energy levels. These energy levels are designated as K, L, M, N and so on.

Some important facts about Structure of atom:

• Almost all of the mass of an atom is in its nucleus, almost all of the volume of an atom is occupied by electrons.
• The particles within an atom are bound together by powerful forces. In general electrons are easier to add and remove.
• The distribution of electrons in various shell or energy levels in an atom is called the electronic configuration of that atom.

The maximum number of electrons that can be accommodated in a shell is given by the formula 2n2 (where n = number of shell i.e. 1, 2, 3--)

Each energy level is further divided into subshells designated as s, p, d, f.

1^st shell (K) contains 1 subshell (s)

2^nd shell (L) contains 2 subshells (s,p)

3^rd shell ( M) contains 3 subshells (s,p,d)

4^th shell (N) contains 4 subshells (s,p,d,f).