Question

give ans for following.

Answer 1

Answer:

i) Atomic no. = total no. of electrons

Atm. no, of P = 2+6 = 8

Atm. no. of Q = 2+8+3 = 13

ii) The number of protons in element Q is 13.

The 27 means the atomic mass is 27.

The number of protons plus the number of neutrons is 27.

That means the number of neutrons is 27–13=14.

iii) Valency of P = 2

Valency of Q = 3

Answer 2

(i) The atomic number of P will be 8 and the atomic number of Q will be 13. The atomic number can be predicted just by calculating the total number of electrons in their shell.

(ii) The number of neutrons in Q will be 14. We can easily calculate the number of neutrons just by subtracting the number of protons by the mass number.

(iii) The valency of element P will be 2- and the valency of element Q will be 3+. The valency can be predicted by having a look at the number of electrons in the outer shell of the atom.

• In the case of P, there are two electrons missing from the outer shell, thus it would need two electrons to make itself stable. (oxygen)
• In the case of Q, there are three electrons present in the outer shell, thus it would need to donate three electrons to make itself stable. (aluminium)