Question

${K^{40}},A{r^{40}},C{a^{40}}$ are:
A. Isobars
B. Isotopes
C. Isotones
D. Isogonals

Answer 1

Hint: Isobars have the same mass number, isotopes have the same atomic number, isotones have the same number of neutrons whereas isogonal have similar angles. ${D^A}$ represents an element with A as mass number.

Complete step by step answer:Any element which is in the form of ${D^A}$ represents an element with D as a symbol and A represents mass number. The mass number of an element is defined as a sum of total number of protons and total number of neutrons in a nucleus. Thus, ${K^{40}},A{r^{40}},C{a^{40}}$ represents the element named potassium, argon and calcium with mass number 40. The atomic number (Z) is defined as the number of electrons in an atom of an element.
Isobars are defined as the atoms of different elements which have the same mass number A but different atomic number Z.
Isotopes are defined as the atoms of the same element which have the same atomic number Z but they differ in their mass number A.
Isotones are defined as the atoms which have different numbers of protons and different numbers of electrons but they have the same number of neutrons.
Isogonals are defined as the figures which have the same angles. It means isogonal polygon, polyhedron, etc.
Hence, ${K^{40}},A{r^{40}},C{a^{40}}$are isobars with the same mass number 40.
Therefore, option A is correct.

Note:The superscript in an element ${Z^A}$ represents mass number (A) and subscript in ${D_Z}$ represents atomic number (Z). The atoms of isobars have the same number of nucleons i.e., same mass number but have different numbers of protons and neutrons.