STRUCTURE OF ATOM
NEUTRONS
In 1932, J. Chadwick discovered another subatomic particle
which had no charge and a mass nearly equal to that of a
proton. It was eventually named as neutron. Neutrons are
present in the nucleus of all atoms, except hydrogen. In
general, a neutron is represented as ‘n’.
The mass of an atom is therefore given by the sum of the
masses of protons and neutrons present in the nucleus
How are Electrons Distributed in Different Orbits (Shells)?
The distribution of electrons into different orbits of an atom
was suggested by Bohr and Bury. The following rules are
followed for writing the number of electrons in different energy
levels or shells:
(i) The maximum number of electrons present in a shell is given
by the formula 2n2 , where ‘n’ is the orbit number or energy
level index, 1,2,3,…
Hence the maximum number of electrons in different shells are
as follows:
first orbit or K-shell will be = 2 × 12 = 2
, second orbit or L-shell will be = 2 × 22 = 8
, STRUCTURE OF ATOM
, third orbit or M-shell will be = 2 × 32 = 18
, fourth orbit or N-shell will be = 2 × 42 = 32, and so on.
(ii) The maximum number of electrons that can be
accommodated in the outermost orbit is 8.
(iii) Electrons are not accommodated in a given shell, unless the
inner shells are filled. That is, the shells are filled in a step-wise
manner.
NEUTRONS
In 1932, J. Chadwick discovered another subatomic particle
which had no charge and a mass nearly equal to that of a
proton. It was eventually named as neutron. Neutrons are
present in the nucleus of all atoms, except hydrogen. In
general, a neutron is represented as ‘n’.
The mass of an atom is therefore given by the sum of the
masses of protons and neutrons present in the nucleus
How are Electrons Distributed in Different Orbits (Shells)?
The distribution of electrons into different orbits of an atom
was suggested by Bohr and Bury. The following rules are
followed for writing the number of electrons in different energy
levels or shells:
(i) The maximum number of electrons present in a shell is given
by the formula 2n2 , where ‘n’ is the orbit number or energy
level index, 1,2,3,…
Hence the maximum number of electrons in different shells are
as follows:
first orbit or K-shell will be = 2 × 12 = 2
, second orbit or L-shell will be = 2 × 22 = 8
, STRUCTURE OF ATOM
, third orbit or M-shell will be = 2 × 32 = 18
, fourth orbit or N-shell will be = 2 × 42 = 32, and so on.
(ii) The maximum number of electrons that can be
accommodated in the outermost orbit is 8.
(iii) Electrons are not accommodated in a given shell, unless the
inner shells are filled. That is, the shells are filled in a step-wise
manner.
