Question

For each of the following species, identify the central atom(s) and propose a hybridization scheme for those \(\operatorname{atom}(\mathrm{s}):(\mathrm{a}) \mathrm{CO}_{2} ;(\mathrm{b}) \mathrm{HONO}_{2} ;(\mathrm{c}) \mathrm{ClO}_{3}^{-} ;(\mathrm{d}) \mathrm{BF}_{4}^{-}\)

Short answer

The central atom and its hybridization for the given species are: (a) CO2: Central atom is C, hybridization is sp. (b) HONO2: Central atom is N, hybridization is sp2. (c) ClO3^-: Central atom is Cl, hybridization is sp3. (d) BF4^-: Central atom is B, hybridization is sp3.

Step-by-step solution

Identify the Central Atom

For each molecule or ion, identify the central atom(s):(a) In CO2, the central atom is C (Carbon).(b) In HONO2, the central atom is N (Nitrogen).(c) In ClO3^-, the central atom is Cl (Chlorine).(d) In BF4^-, the central atom is B (Boron).

Determine the Hybridization

Next, determine the hybridization of each central atom:(a) In CO2, Carbon is double bonded to two Oxygen atoms which leads to a sp hybridization.(b) In HONO2, Nitrogen is bonded to three different groups (one hydrogen, one oxygen double bonded, one O-NO2 group), which is a trigonal planar arrangement and therefore it has sp2 hybridization.(c) In ClO3-, Chlorine is bonded to three oxygen atoms and has one lone pair of electrons which leads to a sp3 hybridization.(d) In BF4^-, Boron is bonded to four Fluorine atoms and so has a sp3 hybridization.

Key concepts

Central Atom Identification

Identifying the central atom in a molecule is the first step in predicting molecular properties. The central atom is usually the one with the most bonding capacity or the least electronegative element, apart from hydrogen.

- In \( CO_2 \), carbon is the central atom because it forms the maximum number of bonds compared to oxygen.
- In \( HONO_2 \), nitrogen is central because of its ability to connect with more atoms, different from the more electronegative oxygens.
- \( ClO_3^- \) features chlorine as the central atom, as it can form bonds with three oxygen atoms effectively.
- Lastly, in \( BF_4^- \), boron is central, capable of linking with all four fluorine atoms effectively.

Central atoms often determine key characteristics of the molecule, like its shape and hybridization.

sp Hybridization

The concept of sp hybridization is related to the linear shape seen in some molecules. This occurs when one s orbital and one p orbital mix, forming two sp hybrid orbitals.

A molecule like \( CO_2 \) exemplifies sp hybridization. Carbon has two double bonds with oxygen, using a linear arrangement.

In sp hybridization, electronic repulsion is minimized as the shape remains linear, typically at an angle of 180 degrees between the bonds. It's often seen in molecules with two domains around the central atom, such as in acetylene. With \( CO_2 \), the carbon atom uses its sp hybrid orbitals to form one sigma bond with each oxygen, while the p orbitals engage in pi bonding.

sp2 Hybridization

sp2 hybridization is common in molecules with a trigonal planar shape. This occurs when one s orbital and two p orbitals combine to form three equivalent sp2 hybrid orbitals.

In \( HONO_2 \), nitrogen is sp2 hybridized, forming a structured arrangement with three bonds.

These three sp2 hybrid orbitals arrange themselves in a trigonal planar shape with an angle of 120 degrees. Elements like ethylene also display sp2 hybridization. In \( HONO_2 \), the nitrogen-coupled system allows for a stable configuration, utilizing one lone pair and three bonds.

sp3 Hybridization

The term sp3 hybridization describes a tetrahedral shape that results when one s and three p orbitals mix, forming four equivalent sp3 hybrid orbitals. This leads to bond angles of about 109.5 degrees.

- In \( ClO_3^- \), chlorine is sp3 hybridized, involving three oxygen bonds and one lone electron pair.
- Likewise, \( BF_4^- \) involves boron sp3 hybridized, forming an organized tetrahedral shape with four fluorine bonds.

sp3 hybridization is common in alkanes and similar molecules. In the case of these polyatomic ions, it's essential for achieving a stable configuration in molecular structures.