A neutral atom possesses an atomic number of 15 and an atomic mass of 31. Three electrons are gained. What is the result of this conversion?

Answer: an anion will form with - 3 charge.

Explanation;

The atomic number of the given atom = 15

Atomic number = number of protons

The number of protons of the given atom = 15

The atomic mass of the given atom = 31

Atomic mass = number of protons + number of neutrons

Hence,

number of neutrons = atomic mass - number of protons

= 31 - 15

= 16

Since, the atomic number is 15, the given atom is P which has the atomic number as 15.

In the neutral compound,

number of protons = number of electrons

Hence,

the number of electrons of the neutral atom = 15

But, the atom has gained 3 electrons.

Gaining of electrons will form anions.

Hence, the atom will be converted into anion which has - 3 charge on it.

But the atomic mass, atomic number, number of protons and number of electrons will not be changed

Neutral atom carries atomic number 15 and atomic mass 31. This is phosphorous (P) atom with 15 electron. We know no. of proton are equal to no. of electron in neutral atom. After gain of 3 electrons, total number of electrons in P atom will change to 18. This results neutral atom onversion into a negative charge ion with a charge of 3-.