Chapter 1, Problem 1.1P

Interpretation Introduction

(a)

Interpretation:

The number of valence electrons found in $\text{Na}$ is to be stated.

Concept introduction:

In an atom, the outermost shell of electrons is the valence shell and the electrons present in this shell are called as valence electrons. For any neutral atom in a group of a periodic table, the number of valence electrons is equal to its group number.

Answer to Problem 1.1P

The number of valence electrons found in $\text{Na}$ is one.

Explanation of Solution

The given atom is sodium. The electronic configuration of sodium is,

$1s^{2}2s^{2}2p^{6}3s^1$

It belongs to the group (IA) of the periodic table. Therefore, it has one valence electron.

Conclusion

Sodium has one valence electron.

Interpretation Introduction

(b)

Interpretation:

The number of valence electrons found in $\text{Ca}$ is to be stated.

Concept introduction:

In an atom, the outermost shell of electrons is the valence shell and the electrons present in this shell are called as valence electrons. For any neutral atom in a group of a periodic table, the number of valence electrons is equal to its group number.

Answer to Problem 1.1P

The number of valence electrons found in $\text{Ca}$ is two.

Explanation of Solution

The given atom is calcium. The electronic configuration of calcium is,

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^2$

It belongs to the group (IIA) of the periodic table. Therefore, it has two valence electrons.

Conclusion

Calcium has two valence electrons.

Interpretation Introduction

(c)

Interpretation:

The number of valence electrons found in ${\text{O}}^{2-}$ is to be stated.

Concept introduction:

In an atom, the outermost shell of electrons is the valence shell and the electrons present in this shell are called as valence electrons. For any neutral atom in a group of a periodic table, the number of valence electrons is equal to its group number.

Answer to Problem 1.1P

The number of valence electrons found in ${\text{O}}^{2-}$ is eight.

Explanation of Solution

The given ion is oxide ion. The electronic configuration of $\text{O}$ is,

$1s^{2}2s^{2}2p^4$

Now, the electronic configuration of ${\text{O}}^{2-}$ is,

$1s^{2}2s^{2}2p^6$

Oxygen belongs to the group (VIA) of the periodic table and with six valence electrons tends to gain two electrons to complete its octet and form the oxide ion, ${\text{O}}^{2-}$ ion. Therefore, oxide ion has eight valence electrons.

Conclusion

The ion, ${\text{O}}^{2-}$ has eight valence electrons.

Interpretation Introduction

(d)

Interpretation:

The number of valence electrons found in ${\text{Br}}^{+}$ is to be stated.

Concept introduction:

In an atom, the outermost shell of electrons is the valence shell and the electrons present in this shell are called as valence electrons. For any neutral atom in a group of a periodic table, the number of valence electrons is equal to its group number.

Answer to Problem 1.1P

The number of valence electrons found in ${\text{Br}}^{+}$ is six.

Explanation of Solution

The given ion is ${\text{Br}}^{+}$. The electronic configuration of $\text{Br}$ is,

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^5$

Now, the electronic configuration of ${\text{Br}}^{+}$ is,

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^4$

Bromine belongs to the group (VIIA) of the periodic table and with seven valence electrons tends to lose an electron to form the ion, ${\text{Br}}^{+}$. Therefore, the ion ${\text{Br}}^{+}$ has six valence electrons.

Conclusion

The ion, ${\text{Br}}^{+}$ has six valence electrons.