Question

An element 'X has mass numbei 35 and number of neutrons 18. Write atomic number and electronic configuration of 'X Also write group number, period number and valency of ‘X'

Answer 1

Answer:

chlorine atomic number is 17

Answer 2

Answer:

Atomic number is 17

Electronic configuration is (2,8,7)

Valency of chlorine is 1

Group number is 7

Period is 3.

Explanation:

Mass number of an element is defined as

Mass number=No.of protons +No.of neutrons

35=No.of protons +No.of neutrons.

35=No.of protons+18

35-18=No.of protons

17=No.of protons.

An element contains 17 protons is having a atomic number of 17, which is chlorine.

Electronic configuration is (2,8,7)

Valency of chlorine is 1 as  it requires 1 electron to complete its orbit.

Group number is defined as number of valence electron in its last shell.so chlorine group number is 7.

Period is defined as number of shells as chlorine has 3 shells so its period is 3.