Question

Draw Lewis structures for the following molecules and ions, and in each case identify the bond order. (Section 4.2 ) \\[\mathrm{Cl}_{2} \quad \mathrm{Se}_{2} \quad \mathrm{HBr} \quad \mathrm{ClO}^{-}\\]

Short answer

Cl₂ has bond order 1; Se₂ has bond order 2; HBr has bond order 1; ClO⁻ has bond order 1.

Step-by-step solution

Drawing Lewis Structure for Cl₂

The Cl₂ molecule consists of two chlorine atoms. Each chlorine atom has 7 valence electrons. Connect the two chlorine atoms with a single bond, sharing a pair of electrons, and complete octets by placing the remaining 6 electrons as lone pairs on each chlorine. The structure is Cl—Cl, where each Cl has three lone pairs. The bond order for Cl₂ is 1, as there is one bond between the two atoms.

Drawing Lewis Structure for Se₂

The Se₂ molecule consists of two selenium atoms, each having 6 valence electrons. Connect the two selenium atoms with a single bond initially. To satisfy the octet rule, place a double bond between them, which uses 4 electrons (2 electron pairs). Fill the remaining 8 electrons as 4 lone pairs (2 on each Se). The bond order is 2, as there is a double bond between the selenium atoms.

Drawing Lewis Structure for HBr

Hydrogen bromide (HBr) consists of one hydrogen atom (1 valence electron) and one bromine atom (7 valence electrons). Connect H and Br with a single bond, using 2 electrons. Place the remaining 6 electrons as 3 lone pairs around Br to fulfill its octet. The bond order for HBr is 1, as there is one bond between H and Br.

Drawing Lewis Structure for ClO⁻

The hypochlorite ion ( ext{ClO}^- ) consists of a chlorine atom and an oxygen atom. Oxygen (6 valence electrons) and chlorine (7 valence electrons) form a single bond using one pair of electrons. To account for the negative charge, add an extra electron, totaling 14 electrons. Distribute the remaining 12 electrons as lone pairs, 6 on Cl and 6 on O, with a single bond still between them. The bond order for ClO⁻ is 1, as there is one single bond between Cl and O.

Key concepts

Chemical Bonding

In the realm of chemistry, chemical bonding is a fundamental concept that describes how atoms come together to form molecules. Essentially, it's the glue that holds atoms together in compounds, allowing them to share or exchange electrons. Chemical bonds typically come in three main types: ionic, covalent, and metallic.

In ionic bonding, atoms transfer electrons to achieve stability, resulting in a connection between oppositely charged ions. Covalent bonding, on the other hand, occurs when atoms share electrons. This sharing of electrons can be equal (nonpolar covalent bonds) or unequal (polar covalent bonds). Lastly, metallic bonds are unique to metals, involving a 'sea' of shared electrons among metal atoms.

These bonds account for the various properties of materials we observe, from the hardness of metals to the solubility of salts. Understanding chemical bonding allows us to predict and explain the structure and reactivity of different substances.

Bond Order

Bond order is a concept used to describe the number of chemical bonds between a pair of atoms. It's a simple count of the number of bonds: single, double, or triple. For example, a single bond has a bond order of 1, while a double bond has a bond order of 2.

Bond order is significant because it provides insight into the bond's strength and length. Typically, a higher bond order means a stronger and shorter bond, whereas a lower bond order implies a longer and weaker bond. For example, the bond order in the Cl₂ molecule is 1 because it involves a single bond between two chlorine atoms. Conversely, the Se₂ molecule has a bond order of 2 due to its double bond.

By understanding the bond order, chemists can glean valuable information about the stability and energy of a molecule, which is paramount when predicting chemical reactions.

Molecular Structure

Molecular structure refers to the three-dimensional arrangement of atoms within a molecule. It tells us how atoms are aligned and connected, significantly influencing the physical and chemical properties of a substance.

When drawing Lewis structures, chemists consider how valence electrons are used to form bonds and satisfy the octet rule, influencing the molecular geometry. A molecule like HBr, for instance, features a straightforward linear structure due to its simple bond. In contrast, more complex molecules may adopt shapes like tetrahedral, trigonal planar, or bent configurations depending on how atoms and electron pairs are arranged.

Understanding molecular structure is crucial for explaining phenomena such as polarity, reactivity, and interaction with other molecules. It is fundamental in fields ranging from pharmaceuticals to materials science, where the shape of a molecule can dictate function and appeal.

Valence Electrons

Valence electrons are the electrons located in the outermost shell of an atom. These electrons are pivotal in the process of chemical bonding as they are the ones involved in forming bonds with other atoms.

Each element has a distinct number of valence electrons, typically corresponding to its group number in the periodic table. For example, chlorine has 7 valence electrons, while selenium has 6, influencing how they bond with other atoms. In the case of ClO⁻, the presence of an extra electron modifies the typical electron count, enabling the formation of its bonds.

Valence electrons are essential for applying rules such as the octet rule, where atoms seek stability by having eight electrons in their outer shell. This quest for stability drives the formation of most chemical bonds, and understanding valence electrons allows chemists to predict how atoms interact and form compounds.