What does below chemistry rebus means?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

People put me on the table and cut me but do not eat me. What am I?

What are the next two letters in the following series and why?
W A T N T L I T F S _ _

*Hint: Check Puzzle Title

At my favorite fruit stand,
an orange costs 18,
a pineapple costs 27,
and a grape costs 15.
Using the same logic, can you tell how much a mango costs?

You Throw The Outside, Cook The Inside
Eat The Outside, Throw The Inside.

What Is It?

How many letters are in the alphabet?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that happen?

Can anyone tell me a word in the English dictionary which has a silent 'z'?

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?