Question

Refer to the following illustration. How many hydrogen atoms could bond with oxygen?

Answer 1

2. 

The reason why is because there are 2 available electron spots on the orbital for the oxygen atom. Hydrogen atoms have one proton and one electron, thus, in order to fill the oxygen atom orbital to a full outer shell, a maximum of 2 atoms could bond with the oxygen atoms. 

6 electrons (oxygen)+ 1 electron (hydrogen)+ 1 electron (hydrogen)= 8 

Answer 2

Answer: The number of hydrogen atoms that can combine to oxygen are 2.

Explanation:

Oxygen is the 8th element of the periodic table with electronic configuration: $1s^22s^22p^4$

This element requires 2 electrons to attain stable electronic configuration.

Hydrogen is the 1st element of the periodic table with electronic configuration: $1s^1$

This element will loose 1 electron to attain stable electronic configuration.

2 Hydrogen atoms will share their 1 electron each with 1 oxygen atom. So, that both the element attain stable electronic configuration.

They will form a covalent compound with chemical formula $H_2O$

Hence, the number of hydrogen atoms that can combine to oxygen are 2.