Explain the dipole moment of $AB_2$ linear molecules (e.g.,$BeF_2$) and $AB_2$ angular molecules (e.g.,$H_2O$).

(N/A) The dipole moment of triatomic $AB_2$ molecules depends on their geometry and the presence of lone pairs on the central atom $A$:
$1$. Linear $AB_2$ molecules:
- These molecules have no lone pairs on the central atom $A$.
- Examples include $CO_2$,$CS_2$,$BeH_2$,$BeCl_2$,and $BeF_2$.
- The bond dipoles are equal in magnitude and point in opposite directions,thus canceling each other out. Consequently,the net dipole moment $(\mu)$ is $0 \ D$.
$2$. Angular $AB_2$ molecules:
- These molecules have lone pairs on the central atom $A$,which causes the molecule to adopt a bent or angular shape.
- Examples include $H_2O$,$NO_2$,$H_2S$,and $F_2O$.
- Due to the angular geometry,the bond dipoles do not cancel each other out. As a result,the net dipole moment $(\mu)$ is not equal to zero $(\mu \neq 0)$. For instance,$H_2O$ has a dipole moment of $1.85 \ D$ and $H_2S$ has $0.95 \ D$.