A stable neutral atom X contains two completely filled orbits. Find out its mass number if it consistsof 10 neutrons. 23. Mass of total positive charge present in an atomis 7348 times to that of the mass of a negativily charged particle. Find the atomic number of an element. Find out its valency.

Explanation

Electronic configuration of X is 2,8
A-Z = number of neutrons A - 10 = 10
`:.` mass number (A) is = 20