Molecule and Molecular Formula

Molecular formula is a presentation of elements that form the compound; likewise, it indicates how many atoms of elements are used. Ex: Water molecule H2O1 has atomicity 3 ; Methane molecule C1H4 has atomicity 5.
Remark: subscript 1 is never written.

Source:

http://www.windows.ucar.edu/physical_science/chemistry/ch4_molecule_big_gif_image.html

Source:
http://www.sciencelearn.org.nz/contexts/icy_ecosystems/sci_media/images/water_molecule

Water molecule in the free conditions, O atom has 2e unpaired and the H-atom has 1e unpaired

Source:

http://commons.wikimedia.org/wiki/File:Electron_shell_008_Oxygen.svg

Source:

http://commons.wikimedia.org/wiki/File:Electron_shell_001_Hydrogen.svg

To be saturated O need 2e & H 1e to become a stable compound. To form a water molecule, these elements bond together in proportion 2H:1O

Source:
http://www.electrical-res.com/hydrogen-and-oxygen-form-water/