Question

The atom of an element X contains 17 protons, 17 electrons and 18 neutrons whereas the atom of an element Y contains 11 protons, 11 electrons and 12 neutrons.

(a) What type of ion will be formed by an atom of element X ? Write the symbol of ion formed.
(b) What will be the number of (i) protons (ii) electrons, and (iii) neutrons, in the ion formed from X ?
(c) What type of ion will be formed by an atom of element Y ? Write the symbol of ion formed.
(d) What will be the number of (i) protons (ii) electrons, and (iii) neutrons, in the ion formed from Y ?
(e) What is the atomic mass of (i) X, and (ii) Y ?
(f) What could the elements X and Y be ?

Answer 1

(a) Element X consists of 17 protons and electrons and 18 neutrons. Element X will readily accept an electron to form a negatively charged anion.
Symbol of the negatively charged X is X⁻.

(b) In the ion formed by X:
(i) Number of protons = 17
(ii) Number of electrons = 18
(iii) Number of neutrons = 18

(c) Element Y consists of 11 protons and electrons and 12 neutrons. Element Y will readily lose an electron to form a positively charged cation.
Symbol of the positively charged Y is Y⁺.

(d) In the ion formed by Y:
(i) Number of protons = 11
(ii) Number of electrons = 10
(iii) Number of neutrons = 12

(e) (i) Atomic mass of X = number of protons of X + number of neutrons of X = 17 + 18 = 35 u

(ii) Atomic mass of Y = number of protons of Y + number of neutrons of Y = 11 + 12 = 23 u

(f) Atomic number of X is 17; therefore, element X is chlorine.
Atomic number of Y is 11; therefore, element Y is sodium.