Question

The third shell (Mshell) of an element X contains 7 electrons. Its mass number is 35.
a) Write the electronic configuration of the clement.
b) What is the atome number of the element?
c) Write the mumber of neutrons in this element
d) Write the symbol of the ion
of this element
​

Answer 1

a) electronic configuration:-

2, 8, 7 ( first type)

1s2 2s2 2p6 3s2 3p5 ( second type)

b) 17 is the atomic no.

c) 35 atomic no.

so neutron = 35- 17= 18

d)Cl- is the ion and Cl is element ( chlorine)

Answer 2

Chlorine has a mass number 35.

• The element has a mass number 35. So, its electronic configuration is-
• ${1s}^{2} {2s}^{2} {2p}^{6} {3s}^{2} {3p}^{5}$
• The atomic number of the element is 17.
• The number of neutrons in the element will be a mass number-atomic number. Thus 35-17=18.

The element has 18 neutrons.

• The element is Chlorine and has the symbol Cl.