If an ion $M^{3+}$ contains $10$ electrons and $14$ neutrons, what are the atomic number and mass number of the element $M$?

Mention the postulates of Niels Bohr put forth to overcome the objections raised against Rutherford's atomic model.

Study the table given below and answer the questions that follow:

Particle	Electrons	Protons	Neutrons
$M$	$2$	$3$	$4$
$N$	$10$	$9$	$10$
$O$	$8$	$8$	$8$
$P$	$8$	$8$	$10$

$(a)$ Write the mass numbers of particles $M, N, O$ and $P$.
$(b)$ Select a cation and an anion from the above table.

$(a)$ Calculate the number of electrons,protons,and neutrons in an atom of an element with atomic number $20$ and mass number $40$. Write the electronic configuration and draw the structure of the atom.
$(b)$ An atom has complete $K$ and $L$ shells. Is this an atom of a metal,non-metal,or noble gas? Justify.

Give the salient features of Rutherford's nuclear model of the atom.

$J. Chadwick$ discovered a subatomic particle which has no charge and has a mass nearly equal to that of a proton. Name the particle and give its location in the atom.