*Between the center of the oxygen atom and the center of the two hydrogens.
In: Chemistry
There are four positions around an oxygen atom that will hold electrons or bonds with other atoms (in this case, hydrogen). Since the atom itself is in a 3D space, the angle between each pair of these spaces is 120 degrees. So when there are two hydrogens bonded to an oxygen, they will sit in two of those spots, making a 120 degree angle. The other two spots are “occupied” by two pairs of oxygen’s native electrons.
The oxygen in the middle has a lone pair of electrons, so the hydrogen repel those electrons. Which causes the angle of 120
Actually it’s an angle of 104.5°. u/Moscau50 has the 3D geometrical picture correct, but because two pairs of oxygen electrons repel the bonding electrons more strongly (think – take up more space) the two O-H bonds get squashed together a little so the angle is a bit less than the 120° that a symmetrical structure would adopt.
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