Question

He (2); Ne (10) and Ar (18) belong to the same group in the modern periodic table (a) Name the period of each element. (b) Write the electronic configuration of each element.

Answer 1

1)
Helium(He) = Period 1
Neon(N) = Period 2
Argon(Ar) = Period 3
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2)
Helium :
Atomic number = 2.
No: of protons =2
No: of electrons = 2
Electronic configuration = 2 , 0


Neon:

Atomic number = 10
No: of protons =10
No: of electrons = 10
Electronic configuration = 2 , 8


Argon:
Atomic number = 18
No: of protons = 18
No: of electrons = 18
Electronic configuration = 2 ,8 , 8

Answer 2

hai friend,
here is your answer

Helium(He) :-

atomic number =2
mass number=4
period number =1
electronic configuration =1s²


Neon(Ne) :-
atomic number =10
mass number=20
period number =2
electronic configuration =1s²2s²2p^6

Argon(Ar) :-
atomic number =18
mass number=40
period number =3
electronic configuration = 1s²2s²2p^63s²3p^6

hope helped:)