Chapter 6.1, Problem 6SSC

Interpretation Introduction

Interpretation:

The two elements of the periodic table which have an atomic mass less than twice their atomic numbers needs to be determined.

Concept introduction:

All the elements have an atomic number. Periodic table is constructed in the increasing order of atomic number. The number of protons of an element represents its atomic number. Atomic mass is the sum of the number of neutrons and protons in the element.

Answer to Problem 6SSC

Two elements of the periodic table which have an atomic mass less than twice their atomic numbers are hydrogen and oxygen.

Explanation of Solution

Hydrogen:

$\begin{array}{l}2\times 1(\text{Atomic}\text{number}\text{of}\text{H)=2}\\ \text{Atomic}\text{mass}\text{of}\text{H=1}\text{.008}\text{amu}\end{array}$

So, atomic mass of hydrogen is less than twice of atomic number.

Oxygen

$\begin{array}{l}2\times 8(\text{Atomic}\text{number}\text{of}\text{O)=16}\\ \text{Atomic}\text{mass}\text{of}\text{O=15}\text{.999}\text{amu}\end{array}$

So, atomic mass of hydrogen is less than twice of atomic number.

Conclusion

Thus, two element hydrogen and oxygen have atomic mass less their twice of the atomic number.