or each of the following pairs, indicate which is smaller.

msp;  a .  Rb + 0 r Na +                                             c .  F − 0 r I − b .  Mg 2 + or Al 3 +                                         d .  Na + or K +

(a)

Interpretation:

The species that is smaller between the given pair is to be predicted and an explanation for the correct choice in terms of electron structure is to be stated.

Concept Introduction:

Cations are always smaller than the atoms from which they are formed because they have lesser number of electrons than the parent atom due to which the force of attraction between protons and electrons increases size decreases.

Anions are always larger than the atoms from which they are formed because they have more number of electrons than the parent atom due to which the repulsion between the electrons increases, the force of attraction between protons and electrons, decreases, and the size increases.

On going down the group, the force of attraction between the nucleus and valence electrons in an atom decreases as the number of shells increases. The size of the atom increases down the group. The same trend goes with the cations or anions of the respective element.

Rb and Na are present in the same group, that is,

(b)

Interpretation:

The species that is smaller between the given pair is to be predicted and an explanation for the correct choice in terms of electron structure is to be stated.

Concept Introduction:

Cations are always smaller than the atoms from which they are formed because they have lesser number of electrons than the parent atom due to which the force of attraction between protons and electrons increases size decreases.

Anions are always larger than the atoms from which they are formed because they have more number of electrons than the parent atom due to which the repulsion between the electrons increases, the force of attraction between protons and electrons, decreases, and the size increases.

(c)

Interpretation:

The species that is larger between the given pair is to be predicted and explanation for the correct choice is to be stated.

Concept Introduction:

Compounds formed from ions are known as ionic compounds. The compound consists of the cation and anion. Cation is the positively charged ion and anion is negatively charged ion.

Cations are always smaller than the atoms from which they are formed because they have lesser number of electrons than the parent atom due to which the force of attraction between protons and electrons increases size decreases.

Anions are always larger than the atoms from which they are formed because they have more number of electrons than the parent atom due to which the repulsion between the electrons increases, the force of attraction between protons and electrons, decreases, and the size increases.

(d)

Interpretation:

The species that is larger between the given pair is to be predicted and explanation for the correct choice is to be stated.

Concept Introduction:

Cations are always smaller than the atoms from which they are formed because they have lesser number of electrons than the parent atom due to which the force of attraction between protons and electrons increases size decreases.

Anions are always larger than the atoms from which they are formed because they have more number of electrons than the parent atom due to which the repulsion between the electrons increases, the force of attraction between protons and electrons, decreases, and the size increases.