This shows a single molecule of water.
We all know that water has the formula H2
Each hydrogen shares an electron with oxygen and this forms a pair of covalent bonds, but the hydrogen atoms are not attached to oxygen in a straight line.
Click to see/ hide more detail about electrons in water
The atomic arrangement means that the water molecule has a partial negative charge (δ-) near the oxygen atom due the unshared pairs of electrons, and partial positive charges (δ+) near the hydrogen atoms. This allows water to form hydrogen bonds (with itself, and other compounds with electronegative atoms) and also explains the special physical and chemical properties of water which are often seen as essential to life.
lone pairs (electron probability envelopes)
MEP - (blue:+ve, red -ve)