Is thallium a transition metal? How do you know?

The minerals found in bones are deposited by living cells called

What are the first two quantum numbers for the electrons located in subshell 4d? what are the first three quantum numbers for the electrons located in subshell 2s? how many electrons can be held in a sublevel l = 3? how many electrons can be held in the energy level n = 4? how many electrons in an atom can share the quantum numbers n = 4 and l = 3?

An atom of which element reacts with an atom of hydrogen to form a bond with the greatest degree of polarity ?