The central atom in H20 is the oxygen atom, 'O'. The oxygen atom has 2 lone pairs of electrons around it, and each lone pair has 2 electrons in it.
2 Hydrogen atoms are in water and 1 oxygen atom
2 H + 1 O = 3 atoms
The H2O molecule (a k a water) consists of 2 hydrogen atoms and one oxygen atom, therefore it consists of 3 atoms and 2 elements.
There is one oxygen atom and two hydrogen atoms.