Chapter EH, Problem 12R

Solution

Interpretation : The data for physical and atomic properties of the group 1 elements based on the trend of increasing atomic number is to be organized.

Concept Introduction : The group 1 elements are also called alkali metals. All these elements have one valence electron.

The properties such as melting point, boiling point, first ionization energy, and electronegativity decrease down the group while the properties such as density and atomic radii increase down the group of alkali metals.

The group 1 elements are lithium, sodium, potassium, rubidium, and cesium.

These alkali metals are metallic and silvery in appearance.

They are soft in nature.

These elements exhibit low density.

Down the group, there is an increase in density, and atomic radii of alkali metals while there is a decrease in melting point, boiling point, first ionization energy, and electronegativity.

Property	Melting point $\left({}^{\text{o}}\text{C}\right)$	Boiling point $\left({}^{\text{o}}\text{C}\right)$	Density $\left(\text{g/mL}\right)$	Atomic radius $\left(\text{pm}\right)$	First ionization energy $\left(\text{kJ/mol}\right)$	Electronegativity (Pauling units)
Lithium	181	1342	0.535	152	520	0.98
Sodium	98	883	0.968	186	496	0.93
Potassium	63	759	0.856	227	419	0.82
Rubidium	39	668	1.532	248	403	0.82
Caesium	28	671	1.879	265	376	0.79