How are elements and compounds diffrent

Need will mark ! which features are created by groundwater erosion and deposition? check all that apply. a. stalagmitesb. sinkholesc. rillsd. stalactites e. gullies f. rivers

The circles, or orbits, for electrons are called energy levels. each level can hold only a certain number of electrons. add electrons to each level until you can't add any more. how many electrons can each level hold?

Which statements explains what the fossil records indicates? check all that apply. a) earth is 4.5 billion years old b) many organisms have become extinct c) mammals have always existed on earth d) mass extinctions have occurred several times on earth e) the amount of water on earth has decreased over time?