Question

Which of the following statements are true if an element shows a valency of '3'?

• A. It can have number of protons equal to '5' inside its nucleus.
• B. It can have number of electrons equal to '5'.
• C. It can have number of protons equal to '7' inside its nucleus.
• D. It can have number of electrons equal to '13' inside its nucleus.

Answer 1

Answer: (A), (B), (C), (D)

The correct options are
A It can have number of protons equal to '5' inside its nucleus.
B It can have number of electrons equal to '5'.
C It can have number of protons equal to '7' inside its nucleus.
D It can have number of electrons equal to '13' inside its nucleus.

Atomic number of an element is number of protons inside its nucleus. Also, we know that number of electrons is equal to number protons. Therefore, Atomic number is also equal to number of electrons.
Therefore, for options (a) and (b), atomic number = 5
Electron distribution for atomic number '5' will be : K = 2, L = 3
Therefore number of electrons in outermost shell = 3
Hence, its valency will be '3'.
Similarly, for option (c), atomic number = 7
Electron distribution for atomic number '5' will be : K = 2, L = 5
Therefore, it will have valency of '3' by gaining three electrons.
For, option (d), atomic number = 13
Electron distribution for atomic number '5' will be : K = 2, L = 8, M = 3
Therefore, it will have valency of '3' by loosing three electrons.