The mass number of an atom whose unipositive ion has 10 electrons and 12 neutrons is :

1. 23
2. 22
3. 20
4. 21

The number of valence electrons in Cl^- ion is:

1. 16
2. 8
3. 17
4. 18

An element 'A' has 15 electrons and 16 neutrons. The correct representation of this element is:

1. ¹⁶₁₅A
2. ³¹₁₆A
3. ³¹₁₅A
4. ¹⁵₁₆A

An atom having 3 protons and 4 neutrons will have a valency of :

1. 3
2. 7
3. 1
4. 4