Question

An atom of element E contains 3 protons, 3 electrons and 4 neutrons :

(a) What is its atomic number?

(b) What is its mass number?

(c) Write the electronic configuration of the element E.

(d) State whether element E is a metal or non-metal. Why?

(e) What type of ion, cation or anion, will be formed by an atom of element E? Why?

(f) Write the symbol of the ion formed by an atom of element E.

(g) What could element X be?

Answer 1

(a) Its atomic number is 3.

(b) Mass no. = 3 + 4 = 7

(c) Electronic configuration is

$\underset{2}{\mathrm{K}}\underset{1}{\mathrm{L}}$

(d) Element E is a metal because in order to complete its octet, the element loses 1 electron from its outermost orbit and attains a stable configuration with 2 electrons in its first shell. Elements which lose electrons to attain stability are called metals.

(e) A Cation will be formed by an atom of element A because its outermost single electron can be easily donated.

(f) E⁺

(g) Element X is lithium.