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 the 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 the 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?

Academic Chemistry NCERT Class 9

(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.

The 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.

The 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.

The atomic number of Y is 11; therefore, element Y is sodium.

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Updated on: 10-Oct-2022

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