What is the period for the following elements? He Ge Rb Eu

Which traits do human embryos have that link them to a common ancestor with fish and reptiles? a. scales and tail b. gill slits and scales c. tail and gill slits d. hair and tail

A5.000 g sample of niso4 h2o decomposed to give 2.755 g of anhydrous niso4. what is the formula of the hydrate? what is the full chemical name for the hydrate? what is the molar mass of the hydrate? niso4•_h2o what is the mass % of water in the hydrate?

How can the periodic table be used to predict the behavior of elements?