Good Riddles

Question: If you lose one of me, you are upset, bewildered, and perplexed.
If you lose two of me, you are blissfully unaware.

What am I?

Question: A very famous chemist was found murdered in his kitchen today. The police have narrowed it down to six suspects. They know it was a two man job. Their names: Felice, Maxwell, Archibald, Nicolas, Jordan, and Xavier.

A note was also found with the body: '26-3-58/28-27-57-16'.

Who are the killers?

Question: You have an 8 by 8 chess board that has two corner squares diagonal from each other removed. Is there any way to place 31 dominoes of size 2x1 to cover the remaining 62 spaces?

Question: I brighten your day but live in the shade.

What am I?

Question: Having one, means having something to follow. Once you question it, it means having none. People seek it, but some do and some don't find it. What is it?