What does below chemistry rebus means?

Look at the below sequence of letters and tell us what the next letter should be:

O T T F F S S ?

Can you name three consecutive days without using the words Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday?

You are stuck on an island where you have nothing. You find four pieces of paper somewhere on the island. What will be your strategy to escape from the island safely?

PS: No other resource is available to you on the island, neither can you build anything.

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

In the picture that is attached with this question, you can find a square which comprises of four little squares inside it. Consider this square to be made with matchsticks. You have to remove two matchsticks such that only two squares remain instead of five.How will you do it ?

How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?

Two old friends, Jack and Bill, meet after a long time.

Three kids
Jack: Hey, how are you, man?
Bill: Not bad, got married and I have three kids now.
Jack: That's awesome. How old are they?
Bill: The product of their ages is 72 and the sum of their ages is the same as your birth date.
Jack: Cool..But I still don't know.
Bill: My eldest kid just started taking piano lessons.
Jack: Oh, now I get it.

How old are Bill's kids?

Can you write down eight eights so that they add up to one thousand?

If you toss a coin 10 times and it lands heads up every time, what are the chances it will land heads up if you toss it again?