Each water molecule consists of two hydrogen atoms bound to one oxygen atom at an angle of 104.5 degrees, giving water its bent shape. The oxygen atom has a partial negative charge while the hydrogen atoms have a partial positive charge, allowing hydrogen bonds to form between the polar water molecules. These hydrogen bonds are relatively weak but plentiful, contributing to water's unique properties.

1. Each molecule of water consists of one atom of oxygen and
two atoms of hydrogen, so it has the chemical formula H2O.
In water, each hydrogen nucleus is bound to the central
oxygen atom by a pair of electrons that are shared between
them; chemists call this shared electron pair a covalent
chemical bond.

2. In H2O, only two of the six outer-shell electrons of oxygen are
used for this purpose, leaving four electrons which are
organized into two non-bonding pairs.
The four electron pairs surrounding the oxygen tend to
arrange themselves as far from each other as possible in order
to minimize repulsions between these clouds of negative
charge.

4. In each water molecule, the nucleus of the oxygen atom (with 8
positively charged protons) attracts electrons much more strongly
than do the hydrogen nuclei (with only one positively
charged proton).
This results in a negative electrical charge near the oxygen atom
(due to the "pull" of the negatively charged electrons toward the
oxygen nucleus) and a positive electrical charge near the hydrogen
atoms.
A difference in electrical charge between different parts of a
molecule is called polarity.
A polar molecule is a molecule in which part of the molecule is
positively charged and part of the molecule is negatively charged.
Because an oxygen atom has a greater electronegativity than a
hydrogen atom, the O―H bonds in the water molecule are polar,
with the oxygen bearing a partial negative charge (δ−) and the
hydrogens having a partial positive charge (δ+).

5. This would ordinarily result in a tetrahedral geometry in
which the angle between electron pairs (and therefore the H-
O-H bond angle) is 109.5°.
However, because the two non-bonding pairs remain closer to
the oxygen atom, these exert a stronger repulsion against the
two covalent bonding pairs, effectively pushing the two
hydrogen atoms closer together.
The result is a distorted tetrahedral arrangement in which the
H—O—H angle is 104.5°.
The water molecule is not linear but bent in a special way. The
two hydrogen atoms are bound to the oxygen atom at an
angle of 104.5°.

6. The O―H distance (bond length) is 95.7 picometres
(9.57 × 10−11 metres, or 3.77 × 10−9 inches).

7. Opposite electrical charges attract one another. Therefore, the
positive part of one water molecule is attracted to the negative
parts of other water molecules.
Because of this attraction, bonds form between hydrogen
positive and oxygen negative atoms of adjacent water
molecules form.
This type of bond always involves a hydrogen atom, so it is
called a hydrogen bond. Hydrogen bonds are bonds between
molecules, and they are not as strong as bonds within
molecules. Nonetheless, they help hold water molecules
together.

8. This bond is very weak. Hydrogen bonds are formed easily
when two water molecules come close together, but are easily
broken when the water molecules move apart again.
They are only a small fraction of the strength of a covalent
bond, but, there are a lot of them and they impart some very
special properties to the substance we call water.
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