Uses Of Periscope
It is used in submarines to determine the distance of a torpedo and helps in deciding the right time for the attack.
It is used in a nuclear reactor to observe the chemical reactions that are taking place.
In military periscopes are used to observe from their hiding position. Hi
If an Atom has 12 Electrons then if it is a Neutral atom then the Atomic Number of the Atom will be 12.
The Electronic Configuration of Element with Atomic Number 12 will be :
⇒ 1s² 2s² 2p⁶ 3s²
We can notice from the Electronic Configuration that :
Given atom has 2 electrons in the 1st shell.
⇒ In the Shell : n = 1
Number of Electrons = 2
In the similar way : Number of Electrons in 2nd shell = 2 + 6 = 8
⇒ In the Shell : n = 2
Number of Electrons = 8
In the similar way : Number of Electrons in 3rd shell = 2
⇒ In the Shell : n = 3
Number of Electrons = 2
Answer:
Ba
Explanation:
Magnesium is the element of second group and third period. The electronic configuration of magnesium is - 2, 8, 2 or
There are 2 valence electrons of magnesium.
Fluorine is the element of seventeenth group and second period. The electronic configuration of fluorine is - 2, 7 or
There is 1 valence electron of fluorine.
They will combine and form 
<u>The same type of compound is formed by the other members of the group 2 since they will have 2 valence electron.</u>
Group 2 includes:- beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).
Hence, correct options is:- Ba