The question refers to the elements of the periodic table with atomic numbers from 3 to 18. In the table below, the elements are shown by letters which are not indicative of the usual symbols of the elements.

At. No.	3	4	5	6	7	8	9	10
Element	A	B	C	D	E	F	G	H
At. No.	11	12	13	14	15	16	17	18
Element	I	J	K	L	M	N	O	P

Which of these is :

1. a noble gas ?
2. a halogen ?
3. an element with valency 4 ?

1. H and P are nobles gases with fully filled valence shells.
2. G and O are halogens having 7 electrons in their outermost orbit.
3. D and L