For each of the following pairs, indicate which species is larger. Explain your reasoning in terms of the electron structure of each species.

msp;  a .  Mg 2 + or Mg           c .  Rb + or Br − b .  Ca 2 + or K +               d .  Se 2 − or Se

(a)

Interpretation:

The species that is larger between the given pair is to be predicted and an 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.

Cations are positively charged and are formed when an atom loses electrons to get stable. Thus, the cations have lesser number of electrons than the parent atom. This results in the increased amount of force of attraction between the nucleus and the electrons in the valence shell as the same number of protons will now attract lesser number of electrons. This results in decrease in size of the cation. Thus the cations are always smaller than the atom from which they are formed...

(b)

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.

(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:

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.