What does below chemistry rebus means?

I am five letter word that is under you.
If you remove my 1st letter, then I am over you.
If you remove my 1st and 2nd letters then I am all around you.

Who am I?

Dr Doom invited a group of puzzle fanatics to a party which was oriented toward having puzzle-oriented games. At night, he introduced the guests to a 'unique riddle'. A prize was offered to the one who solved it first.

The guests included six people named Tom Paul, Fox Obama, Jeremy Reener, Alex Murphy, Prim Pastor, and Ellen Page. The winner of the 'unique riddle' contest was to be announced after the dinner. So Dr. Doom stood up and started the announcement:

'Okay now everybody!'
'The winner of�'
'The Hardest Riddle Ever Event'

But before he could complete it, the light went out and his voice was not heard without the mic by anyone. But they already knew who the winner was. Can you deduce the name of the winner?

How many squares, of any size, can you find on this chessboard which do not contain a Rook?

Things are just as they seem, right? Well, check again.
Can you count the number of tigers in this picture ?

I have a head like a cat and feet like a cat, but I am not a cat. What am I?

What is Luis Suarez's (Soccer Player) favorite tea?

How many words can a quill made with the feather of a pigeon write with a 100ml bottle of black ink?

Mr Red Lives in the red house.
Mr Green Lives in the greenhouse.
Mr Yellow Lives in the yellow house.

Who lives in the Whitehouse?

What is next number in the pattern below:

131 517 192 123 ?