Question

Three different atoms of oxygen are represented as : 
`""_8^16"O"`, `""_8^17"O"`, `""_8^16"O"`
(i) What do the subscripts (lower figures) and superscripts (upper figures) represent ?
(ii) What factor is responsible for the change in the superscripts 16, 17 and 18, though the element is the same ?
(iii) What is the usual name for such atoms of an element ?
(iv) Give the nuclear composition of  `""_8^16"O"`.

Answer 1

(i) Subscript represents atomic number, whereas superscript represents atomic mass.
(ii) Number of neutrons is responsible for the change in superscripts.
(iii) Isotope is the usual name for such atoms of an element.
(iv) Nuclear composition of `""^18"O"_8` is -
No. of protons = 8
No. of neutrons = 18 − 8 = 10