Question

An element X has mass number 35 and the number of neutrons is 18. Identify the group number and period of X ...

Answer 1

Given :
Mass number of element is 35
Number of neutrons= 18

Formula to find number of protons: 
Mass number = number of protons + number of neutrons.
35=× +18
×=35 - 18
X=17.
Number of protons =17 and number of electrons also will be 17 as atom is electrically neutral.

Hence Element is chlorine

Electronic configuraton:
1s2 2s2 2p6 3s2 3p5

Group number= 17
Period number =3
Valency =1

Answer 2

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