Chapter 21, Problem 21.1VP

Interpretation Introduction

Interpretation: The part of Figure P21.1 that best describes the periodic trend in monatomic cation radii moving up or down a group or across a period in the periodic table is to be stated.

Concept introduction: On moving up to down in a group, the principal quantum number ‘n’ increases. Number of shells of electrons increases down the group. Therefore, the size of cation increases down the group.

To determine: The part of Figure P21.1 that best describes the periodic trend in monatomic cation radii moving up or down a group or across a period in the periodic table.

Answer to Problem 21.1VP

Solution

The part of Figure P21.1 that best describes the periodic trend in monatomic cation radii moving up or down a group or across a period in the periodic table is part (d).

Explanation of Solution

Explanation

The periodic trends in monatomic cation radii moving up or down a group or across a period in the periodic table are shown below.

Figure 1

A cation is formed when a neutral atom loses an electron. When an electron is lost, the electron-electron repulsion in an atom decreases. Hence, the interaction between nucleus and valence electrons increases. Therefore, the size of cation is less than the corresponding atom

On moving up to down in a group, the principal quantum number ‘n’ increases. Number of shells of electrons increases down the group. Therefore, the size of cation increases down the group. On moving right to left, the principal quantum number remains the same but the effective nuclear charge of electron increases. The atomic number of elements decreases. Therefore, the atomic radii of cation also increase on moving right to left across period.

The part that describes the trend in monatomic cation radii moving up or down a group or across a period in the periodic table is part (d) because in this part, cationic radii is increasing on moving down the group and on moving right to left in a period.

Conclusion

The part of Figure P21.1 that best describes the periodic trend in monatomic cation radii moving up or down a group or across a period in the periodic table is part (d).