What information do you know from `._(17)^(35)X` ?

Explanation

Given that `._(17)^(35)X`
a) The atomic number of element is 17.
b) Hence the element is chlorine, symbol is `'Cl'.`
c) Number of protons = 17.
d) Number of electrons = 17.
e) Mass number = 35.
f) Number of neutrons `=37-17=18`
g) Distribution of electrons in shells
`{:(K,L,M,N),(2,8,7,-):}`
h) Valency is '1'.
It gains one electron to become octet.