Question

From the following find out groups of isotopes, isobars and isotones:
${}_{8}^{16}O,{}_{19}^{39}K,{}_{6}^{14}C,{}_{92}^{239}U,{}_{7}^{14}N,{}_{20}^{40}Ca,{}_{92}^{238}U,{}_{32}^{77}Ge,{}_{33}^{77}As,{}_{8}^{18}O,{}_{32}^{76}Ge,{}_{34}^{78}Se$

Answer 1

Hint: 1. Isotopes have the same atomic number but different mass number.
2. Isotones have mass number of neutrons where,
Number of neutrons = Mass number – number of protons
3. Isobars have the same mass number but different atomic number.
4. ${}_{Atomic\,no.}^{Mass\,no.}Z$ is the general representation of an element.

Complete step-by-step answer:

1. Isotopes:
${}_{32}^{76}Ge$ and ${}_{32}^{77}Ge$
${}_{92}^{239}U$ and ${}_{92}^{238}U$
${}_{8}^{16}O$ and ${}_{8}^{18}O$

2. Isotones:
${}_{19}^{39}K$and ${}_{20}^{40}Ca$ and ${}_{8}^{18}O$ all of them have $10$ neutrons.
${}_{8}^{16}O$ and ${}_{6}^{14}C$ both of them have 8 neutrons.
${}_{33}^{77}As$ and ${}_{32}^{76}Ge$ and ${}_{34}^{78}Se$ all of them have $44$ neutrons.

3. Isobars:
${}_{6}^{14}C$ and ${}_{7}^{14}N$
${}_{32}^{77}Ge$ and ${}_{33}^{77}As$

Note: Isotopes are two or more chemical species of atoms of an element with the same atomic number and position in the periodic table and nearly identical chemical properties but with different atomic masses and physical properties.
Isotones are two or more species of atoms or nuclei that have the same number of neutrons but different number of protons and different mass numbers. For example, chlorine- and potassium- are isotones, because the nucleus of this species of chlorine consists of protons and neutrons, whereas the nucleus of this species of potassium contains protons and neutrons and both have the same number of neutrons.
Isobars are atoms of different chemical elements that have the same number of nucleons i.e. neutrons + protons. Hence, isobars differ in atomic number (or number of protons) but they have the same mass number or same number of nucleons.