Question

What is the steric number for the O atom in water?

Answer 1

Hint: Water ($$H_{2}O$$) is an inorganic, clear, tasteless, odourless, and virtually colourless chemical substance that is the primary ingredient of the Earth's hydrosphere and all known living species' fluids (in which it acts as a solvent). Even though it contains no calories or organic nutrients, it is necessary for all known forms of life. Each of its molecules has one oxygen and two hydrogen atoms linked by covalent bonds, as indicated by its chemical formula $$H_{2}O$$.

Complete answer:
The number of atoms bound to a central atom of a molecule plus the number of lone pairs connected to the core atom is known as the steric number. VSEPR (valence shell electron pair repulsion) theory uses a molecule's steric number to predict its molecular geometry. The VSEPR theory uses simpler ideas than the more complicated original methods to calculate the form of a molecule, or its geometry. It's beneficial for predicting the shapes of molecules with a core atom that's bonded to numerous other atoms on all sides. It's also used to figure out which of several products will be the end result of an organic process.
This means that all you have to do to determine an atom's steric number is count how many lone pairs of electrons it has and how many bonds it makes with other atoms.
Drawing the Lewis structure of water, $$H_{2}O$$, is an excellent place to start.

Each water molecule has two hydrogen atoms and one oxygen atom. There will be a total of 8 valence electrons in the molecule.
one atom of hydrogen from each of the two hydrogen atoms
six from the presence of oxygen
The centre atom will be the oxygen atom. It will make two single bonds, one with each hydrogen atom, accounting for four valence electrons, and it will have two lone pairs of electrons accounting for the remaining four.
The oxygen atom is surrounded by four electron density areas, two single bonds, and two lone pairs of electrons, as shown.
As a result, the steric number of the atom will be equal to 4.

Note:
The assumption of VSEPR is that the valence electron pairs around an atom resist each other and, as a result, would organise themselves in a way that minimises this repulsion. This reduces the energy of the molecule and enhances its stability, determining the molecular shape. The electron-electron repulsion caused by the Pauli exclusion principle is more significant than the electrostatic repulsion in defining molecule geometry, according to Gillespie.