What does below chemistry rebus means?

Railroad Crossing, look out for the cars. Can you spell that, without any R's ?

The more you take me, the more you leave me behind.
Who Am I?

The richest man in the city Mr Rechard is kidnapped. James Bond is appointed to the case. At the crime scene, a note is found written by Mr Richard. The note read:

"First of January, Fourth of October, Fifth of March, Third of June."

James Bond knew that somehow, the killer's name was hidden in the note. The following were the suspects:

Jack Richard, the son and the heir of property.
John Jacobson, the employee of Richard.
June Richard, the wife of Richard.

James Bond took only a few moments to deduce the killer's name. Can you tell who was the killer?

John named his first son Alpha, second Beta, third Charlie and fourth Delta. What is the fifth son's name?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

what does the below rebus means?

If your uncle’s sister is not your aunt, what relation is she to you?

Different lights make me strange by changing me into different sizes. What am I?

Find the next number in the sequence

1, 2, 6, 21, 88, __?