Chapter 10, Problem 207A

Interpretation Introduction

Interpretation:

Atomic number and mass number must be contrasted. These numbers must be compared for isotopes of an element.

Concept introduction:

Atomic number is the number of protons of the atom of an element.

Mass number is the sum of protons and neutrons of the atom of an element.

Answer to Problem 207A

Atomic number doesn’t include neutrons but mass number includes neutrons.

For isotopes of an element, atomic number is same but mass number is different.

Explanation of Solution

Atomic number is generally expressed by Z and mass number is expressed by A.

For ₈O¹⁶, atomic number (Z) is 8. It means there are 8 electrons, 8 protons in one atom of oxygen. Mass number (A) is 16 which includes 8 protons and 8 neutrons.

If all the isotopes of oxygen are considered then there will same atomic number but different mass number. ₈O¹⁶, ₈O¹⁷ and ₈O¹⁸ all have same atomic number 8 and mass numbers are 16, 17 and 18 respectively.

Conclusion

For isotopes of an element atomic number is same but mass number is different.