According to dictionary. com, one definition of the word "sphere" is: the place of environment within which a person or thing exists using this definition along with your descriptions of the prefixes geo, bio, hydro and atmos, define the following terms:
1. geosphere
2. biosphere
3. hydrosphere
4. atmosphere

the answers would be

the first one and the second one

2b2t

explanation:

2b2t

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

if you need further assistance, let me know: )

~ trueboss72