Question

${}_{19}{K}^{40}$ and ${}_{20}C{a}^{40}$ are known as

• A. isotopes
• B. isobars
• C. isotones
• D. Isodiaphers

Answer 1

Answer: (B)

Isotopes: They are atoms of same element which have same atomic numbers but different atomic masses, eg, ${}_{\text{1}}^{\text{1}}{\text{H,}}_{\text{1}}^{\text{2}}\text{H}$ and ${}_{\text{1}}^{\text{3}}\text{H}\text{.}$ Isobars: They are atoms of different elements which have different atomic numbers but similar atomic masses. Isotones: These are atoms of different elements which have same number of neutrons. Their atomic numbers and atomic masses both are different, eg, ${}_6^{12}C$ and ${}_{\text{7}}^{\text{15}}\text{N}\text{.}$ ${}_{\text{19}}^{\text{49}}\text{K}$ and ${}_{\text{20}}^{\text{49}}\text{Ca}$ are isobars because they have same atomic mass (40).