What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

I am written with two letters.
I said with the one.
I usually am seen with the two.

Who am I?

When does a USA Potato change its nationality?

When you say goodbye, I am what you need to tie.
I come as a couple and go wherever you run.
Who am I?

Can you find the largest Three-digit number whose sum is 14 and whose square is less than 5,00,000?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

From a pack of 52 cards, I placed 4 cards on the table.

I will give you 4 clues about the cards:

Clue 1: Card on left cannot be greater than the card on the right.
Clue 2: Difference between the 1st card and 3rd card is 8.
Clue 3: There is no card of an ace.
Clue 4: There are no face cards (queen, king, jacks).
Clue 5: Difference between the 2nd card and 4th card is 7.

Identify four cards?

Which word is least like the others? Third, fourth, fifth, sixth, seventh, eighth, ninth?

A man started to town with a fox, a goose, and a sack of corn. He came to a stream which he had to cross in a tiny boat. He could only take one across at a time. He could not leave the fox alone with the goose or the goose alone with the corn. How did he get them all safely over the stream?

There are two insects on a tile. Insect X is sitting on one side of the tile (point A) and Insect Y is sitting opposite on the other side of the tile (point B). Now both of them decide to change their position and thus X starts crawling to point B and Y starts crawling to point A. When they meet and pass each other in between, X takes 20 seconds to reach B and Y takes just 5 seconds to reach A.

Can you calculate the total time each of the insects took to change their positions?