Chapter 7, Problem 52A

Interpretation Introduction

Interpretation: A table needs to be constructed to show the relation between group number, valence electrons lost or gained, and formula of cation or anion formed for given elements.

Concept Introduction: In a periodic table, group number gives the total number of valence electrons present in an atom of the element. Whether an element gains or loses electron/s depends on its number of valence electrons or group number. It also depends on the nature of the element that is whether it is metallic or non-metallic. Metallic elements tend to lose electrons to form cations. Non-metallic elements tend to gain electrons to form an anion.

Explanation of Solution

The given elements are Na, Ca, Al, N, S, and Br. Here, Na, Ca, and Al is metallic elements thus, they lose electrons. Similarly, N, S, and Br are non-metallic elements thus, they gain electrons. The group number is related to the number of valence electrons. Here, metallic elements lose electrons to form positive charge ions, and the charge on the ion is equal to the number of electrons lost. Similarly, the charge on an anion is equal to the number of electrons gained by non-metallic elements.

The below table shows the relationship between the group number, valence electrons lost or gained, and the formula of cation or anion formed for given elements.

Elements	Group number	Valence electrons lost or gained	Formula of cation and anion formed.
Na	1	1 (lost)	${\text{Na}}^{+}$
Ca	2	2 (lost)	${\text{Ca}}^{2+}$
Al	3	3 (lost)	${\text{Al}}^{3+}$
N	15	3 (gained)	${\text{N}}^{3-}$
S	16	2 (gained)	${\text{S}}^{2-}$
Br	17	1 (gained)	${\text{Br}}^{-}$