What is Murcury's atmosphere like?

Mercury's atmosphere is very thin. The atmosphere of Mercury is mainly made out of sodium. Mercury's atmosphere is so thin because the gases that were there before all got boiled by the sun. The thin air does not trap heat very well. So, Mercury is actually not as hot as Venus. Part of Mercury's surface can rise to 800°F and part of Mercury can go down to -300°F. This can happen because in the day time the Sun heats up Mercury's surface quickly and at night time Mercury loses most of its heat. With no air and no clouds, Mercury's weather is always the same, extremely hot in the day and extremely cold in the night.