Answer:
The correct answer is X
Step-by-step explanation:
First have some idea about : Valency , Metals and non- metals.
Valency : It is the combining capacity of elements . The elements combine to other elements to gain stability . They always try to complete their octet(8 electrons in the outermost shell)
For Example : Na has 11 electron
Its electronic configuration is : 2 ,8 ,1 (2+8+1 = 11)
First shell contain maximum = 2 electron
2nd shell = maximum 8 electron
3 shell = maximum 18 electron
When it remove 1 electron from outermost shell , it is left with 2 ,8 configuration. Now , its outer most shell has 8 electron . so it get stable and show +1 valency.
When the element looses electron , it get positive charge
When the element gain electron it get negative charge
Metals: those element which show +1 , +2 , +3 valency are considered as metals
Non- metals = Those metals which show the valency of -1 , -2 ,-3 are considered as Non- Metals.
Questions:
1. T = 7 proton
Electronic configuration = 2 , 5
It gains (-ve charge) 3 electron to achieve complete octet(5+3 = 8) = -3 valency
It is non- metal
2. Q=15
Its electronic configuration = 2 ,8 , 5
It gains (-ve charge) 3 electron to achieve complete octet(5+3 = 8) = -3 valency
It is non- metal
3.X = 12
Its electronic configuration = 2 ,8 , 2
It loses (+ve charge) 2 electron to achieve complete octet( 2 , 8) = + 2 valency
It is metal
4.Z = 17
Its electronic configuration = 2 ,8 , 7
It gains (-ve charge) 1 electron to achieve complete octet(7+1 = 8) = -1 valency
It is non- metal
There is only one metal = X