JAMB Physics 2017 Paper

Concept:Every atom is represented by its mass number at the top left and its atomic number at the bottom left.Explanation:For a neutral atom, the number of electrons equals the number of protons.So the number of protons in atom X is $28$.The atomic number is therefore $28$.The mass number is the sum of protons and neutrons.Mass number $= 28 + 30 = 58$.Hence X is written as $^{58}_{28}X$.Answer:The correct representation is $^{58}_{28}X$.This matches Option A.