Edwin Hubble found out that were appear to be large clouds in space were not gas but

he spotted a cepheid variable star that was known as the andromeda nebula.  he showed that andromeda was nearly 1 million light years away and was a galaxy in its own right, not a gas cloud.

with this one i know the answer in craters one reason i looked it up and i learned about it there is my evidence

each chemical family is represented as a group or column on the periodic table. based on chemical properties, there are 6 types of chemical families. group 1 represents alkali metals, group 2 represents alkaline earth metals, groups 3 to 12 represent transition metals, groups 13 to 16 represent non-metals and other metals, group 17 represents halogens and group 18 represents noble gases.