Chemical Bonding And Molecular Structure

A Lewis acid is a substance that can accept a pair of electrons. In the case of molecular hydrides:
- (Ammonia) is a Lewis base because it has a lone pair of electrons on nitrogen that can be donated.
- (Water) is also a Lewis base due to the lone pairs on oxygen.
- (Diborane) acts as a Lewis acid because boron atoms in diborane have an incomplete octet and can accept electron pairs.
- (Methane) does not act as a Lewis acid because it does not have an empty orbital to accept electron pairs.
Thus, (Diborane) is the only hydride that acts as a Lewis acid.

The order of polarity, from least polar to most polar, among the given molecules is as follows:

1. CO2 (Carbon dioxide) - Nonpolar molecule due to its linear arrangement and the symmetry of its bonds.
2. HCl (Hydrogen chloride) - Polar molecule due to the electronegativity difference between hydrogen and chlorine.
3. H2O (Water) - Highly polar molecule due to the bent molecular geometry and the significant electronegativity difference between hydrogen and oxygen.
4. HF (Hydrogen fluoride) - Highly polar molecule due to the strong electronegativity difference between hydrogen and fluorine, similar to water

Order of increasing polarity is CO2 < HCl < H2O < HF

An ionic bond arises exclusively in situations where one of the participating atoms is a metal, while the other is a non-metal. For this bond to manifest, the metal atom must possess a low ionization energy, enabling the effortless emission of electrons, ultimately leading to the creation of a cation. Conversely, the non-metal counterpart necessitates a notably elevated electron affinity, which serves to draw in the electron, facilitating the formation of an anion.

Conditions are:
1) An ionic bond is formed only when one of the atoms is metal and the other is non-metal.
2) The metal atom must have low ionization energy so that it can release electrons easily and form a cation.
3) The non-metal should have a high value of electron affinity to attract the electron to form an anion.

To determine which molecule has a linear shape, we need to consider the molecular geometry. Molecular geometry is influenced by the number of bond pairs and lone pairs of electrons around the central atom, according to VSEPR (Valence Shell Electron Pair Repulsion) theory.

Let's analyze each molecule:

• H₂O: Water has two hydrogen atoms bonded to an oxygen atom. Oxygen has two lone pairs of electrons. The molecular shape is bent due to electron pair repulsion, not linear.
• CO₂: Carbon dioxide consists of a carbon atom double-bonded to two oxygen atoms. No lone pairs on the carbon. The bonds are distributed symmetrically, resulting in a linear shape.
• NH₃: Ammonia has three hydrogen atoms bonded to a nitrogen atom with one lone pair, giving it a trigonal pyramidal shape, not linear.
• SO₂: Sulfur dioxide consists of a sulfur atom bonded to two oxygen atoms and has a lone pair, leading to a bent shape, not linear.

Based on this analysis, CO₂ is the molecule with a linear shape.

To determine which of the given molecules has a trigonal planar shape, we first need to understand the concept of molecular geometry. The shape of a molecule is determined by the arrangement of atoms around the central atom, which is influenced by the electron-pair repulsion theory, often called the VSEPR (Valence Shell Electron Pair Repulsion) theory.

VSEPR Theory: The shape of a molecule is determined by the repulsions between electron pairs in the valence shell of the central atom. These pairs arrange themselves as far apart as possible to minimize repulsions.

Analyzing each molecule:

• : Methane has a central carbon atom with four hydrogen atoms, leading to a tetrahedral geometry due to four bonding pairs.
• : Boron trifluoride has a central boron atom with three fluorine atoms. The three bonding pairs and absence of lone pairs on boron result in a trigonal planar shape.
• : Ammonia has a central nitrogen atom with three hydrogen atoms and one lone pair of electrons, leading to a trigonal pyramidal shape.
• : Water has a bent shape because of two hydrogen atoms attached to oxygen and two lone pairs on the oxygen.

Thus, the molecule with a trigonal planar shape is .