Question

What is the VSEPR model for $C{O_2}$ ?

Answer 1

The arrangement of atoms in simple and symmetric molecules are determined by VSEPR theory. The central metal atom and terminal atoms arrangement and bonded electrons, lone pairs geometry can be explained by this theory. Based on the central metal atom and lone pairs, bonded electrons carbon dioxide is $A{X_2}$ system.

Complete answer:
Carbon dioxide is the molecule consisting of carbon and two oxygen atoms. The valence electrons of carbon are $4$ and the valence electrons of the oxygen atom is $6$ and the two oxygen atoms have $12$ electrons. The total valence electrons of carbon dioxide are $16$ electrons. Out of these $16$ electrons, eight electrons are bonded pairs of electrons and the remaining eight electrons are existing as lone pairs of electrons on oxygen atoms due to the electronegativity of oxygen.
VSEPR theory stands for valence shell electron pair repulsion. According to this theory, bonding and non-bonding electrons of the central metal atom in a molecule will repel each other and give the molecular shape.
Some notations were given by this theory to explain the geometry of the molecule:
$A{X_2}$ linear
$A{X_3}$ trigonal planar
$A{X_3}E$ trigonal pyramidal
$A{X_2}{E_2}$ bent
$A{X_4}$ tetrahedral
Carbon dioxide has $A{X_2}$ notation, as A is the central metal atom which is carbon and X is the terminal atom which is oxygen.
Thus, according to VSEPR theory, $C{O_2}$ is linear.

Note:
The lone pair of electrons on the central metal atom is also responsible for the prediction of geometry of molecules. In the molecule of carbon dioxide, there were two lone pairs of electrons on each oxygen atom, but not lone pairs on central metal atom carbon. Thus, it belongs to $A{X_2}$ notation.