What does below chemistry rebus means?

During a secret mission, an agent gave the following code to the higher authorities
AIM DUE OAT TIE MOD

However, the information is in one word only and the rest are fake. To assist the authorities in understanding better, he also sent them a clue, If I tell you any one character of the code, you can easily find out the number of vowels in the codeword.

Can you find out the code word?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

A beggar on the street can make one cigarette out of every 6 cigarette butts he finds. After one whole day of searching and checking public ashtrays the beggar finds a total of 72 cigarette butts. How many cigarettes can he make and smoke from the butts he found?

A Doctor always sneezes before the rain. Doctor sneezes, Will it rain?

Why did Buffon take the goal with him after every Juventus match?

Get total of 120 by using five zeros 0,0,0,0,0 and any one mathematical operator.
Do you ?

What is black when you buy it, red when you use it, and gray when you throw it away?

A charming young lady was approached by a kind looking old woman in a restaurant. The old woman said to her, 'You look exactly like my younger daughter. Sadly she passed away a couple of months back. Could you do me a favor and say 'Goodbye, mother' with a kind smile on your face when I leave?

The young lady agreed for the same and said, 'Goodbye, mother' when the old woman left. Soon after, she got the most disengaging shock of her life.

Can you guess what the shock was?