State how hydrogen occurs in the free state. Name three compounds containing hydrogen in the combined state.

Where does hydrogen occur in free state ?

State how carbon occurs in the free state and in the combined state,

Boron does not occur in the free state. Why?

Hydrogen peroxide , in the pure state is

State three precautions taken in preparing hydrogen.

Can hydrogen exist in -1 oxidation state?

Metals which occur in free state. ………… , …………

What is the energy of a hydrogen atom in the first excited state if the potential energy is taken to be zero in the ground state?

What is the energy of a hydrogen atom in the first excited state if the potential energy is taken to be zero in the ground state?

What type of elements are found to occur in the combined state?