Chapter 11, Problem 72A

(a)

Interpretation Introduction

Interpretation:

The nuclear charge of the element needs to be calculated.

Concept Introduction:

The nuclear charge is equal to the number of protons.

The mass number is the sum of protons and neutrons. And hence,

  $\text{number of protons}=\text{ atomic mass }-\text{ number of neutrons}$

Answer to Problem 72A

The nuclear charge of the element is $80$ .

Explanation of Solution

Here,

 • $\text{atomic mass of the element}=203$

 • $\text{number of neutrons}=123$

  $\begin{array}{c}\text{ Number of protons}=\text{ 203}-123\\ =80\end{array}$

(b)

Interpretation Introduction

Interpretation:

The symbol and name of the element need to be determined.

Concept Introduction:

The atomic number of an element is equal to the number of protons. From the atomic number, symbol and name can be obtained.

Answer to Problem 72A

The symbol of the element is Hg and the name of the element is Mercury

Explanation of Solution

  $\text{Proton number of the element}=80$

Hence, the atomic number of the element is also $80$ .

The atomic number $80$ corresponds to the mercury atom.

(c)

Interpretation Introduction

Interpretation:

The number of valence electrons is to be determined.

Concept Introduction:

For the neutral atom,

  $\text{number of protons }=\text{number of electrons}$

From electronic configuration, valence electrons can be determined.

Explanation of Solution

The electronic configuration of Hg is $[\text{Xe}]4f^{14}5d^{10}6s^2$ .

Valence electrons are outer electrons of the shell. So, for Hg, valence electrons are two.

(d)

Interpretation Introduction

Interpretation:

The energy level is to be determined.

Concept Introduction:

The number of energy levels is the possible levels around the nucleus where electrons are present. It depends on the period number of an element. For example, elements in the 1^st period have 1 energy level, elements in the 2^nd period have 2 energy levels and so on.

Answer to Problem 72A

The number of energy levels is 5.

Explanation of Solution

The number of electrons in a neutral atom is 40 thus, the electronic configuration will be:

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

Since the outermost electron is present in the 5^th shell, thus; the number of energy levels will be 5.