Answer: The number of hydrogen atoms that can combine to oxygen are 2.
Step-by-step explanation:
Oxygen is the 8th element of the periodic table with electronic configuration:
![1s^22s^22p^4](https://img.qammunity.org/2019/formulas/chemistry/high-school/ai35lwtl8onqd0hfcl95np2lgx9sivy464.png)
This element requires 2 electrons to attain stable electronic configuration.
Hydrogen is the 1st element of the periodic table with electronic configuration:
![1s^1](https://img.qammunity.org/2019/formulas/chemistry/high-school/dsv4b27lin7mu641acdpjs2gfh03ek2i4b.png)
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](https://img.qammunity.org/2019/formulas/chemistry/high-school/6hlutk8606w2ok5nx8qbbytaae8khf510v.png)
Hence, the number of hydrogen atoms that can combine to oxygen are 2.