Question

How can we identify that an element is metal or non metal?

Use can take the above picture as reference. The question is asked in (b)(iv)

Answer 1

(b). atomic no. of y element is 17
ec = 2,8,7
ve= 1.
therefore this is a meta beacouse we know that the element whose ve is 1,2&3. they are generally metals.

Answer 2

you should know the element first and the atomic no. the according to the electronic configuration you should know that the last no. of electron which is in the outermost orbit I,e. 1,2,3,4,5,6,7,8 . upto 1234 which have the valancy that are metal and 4,5,6,7, you should substract from 8 then you will get the non metal . Hope you get it.