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) The mass number of an atom is the sum of the number of protons and neutrons in its nucleus.
$M: 3 + 4 = 7$
$N: 9 + 10 = 19$
$O: 8 + 8 = 16$
$P: 8 + 10 = 18$
$(b)$ $A$ cation is a positively charged ion formed by the loss of electrons (number of protons > number of electrons). In particle $M$,protons = $3$ and electrons = $2$,so it is a cation.
An anion is a negatively charged ion formed by the gain of electrons (number of electrons > number of protons). In particle $N$,electrons = $10$ and protons = $9$,so it is an anion.