a. Hydrogen and oxygen react to form water, \(\mathrm{H}_{2} \mathrm{O}\). Draw a Lewis diagram for water using the line-bond shorthand. b. Draw the Lewis diagram for the molecules, hydrogen chloride, \(\mathrm{BrCl}\), and hydrogen cyanide (HCN).

Chemical bonding is the force that holds atoms together in molecules and compounds, forming a stable structure. Understanding chemical bonds is crucial for deciphering how atoms combine to form substances with unique properties. The types of chemical bonds primarily include ionic, covalent, and metallic bonds.

In a covalent bond, such as those found in water (H₂O), atoms share electrons to achieve a full outer shell, leading to stable molecules. For example, each hydrogen atom in water shares an electron with oxygen, resulting in two covalent bonds. Similarly, in hydrogen chloride (HCl) and hydrogen cyanide (HCN), the atoms are bonded covalently by sharing electrons. Single lines between atoms in Lewis structures represent single bonds, while double or triple lines represent double or triple bonds, indicative of multiple electron sharing between atoms.

The strength and number of bonds impact a molecule's properties and behaviors. For instance, the triple bond in hydrogen cyanide makes it more rigid and less reactive than molecules with single bonds. By mastering the concept of chemical bonding, students can predict how atoms will interact and what type of bond they will form, which is essential to the understanding of chemical reactions.

Valence electrons are the electrons in the outermost shell of an atom that are involved in forming bonds. They are the key players in chemical bonding because they facilitate interaction between atoms. To draw Lewis structures accurately, one must first count the number of valence electrons an atom has.

For instance, in the Lewis structure for water, oxygen has six valence electrons while hydrogen has one each. The ability of valence electrons to participate in bonding determines the reactivity of an element: the more open spaces in the outer shell, the more eager the atom is to react and form bonds.

• Oxygen has two open spaces, allowing it to form two bonds with hydrogen.
• Chlorine has one open space, and it forms one bond with hydrogen in HCl.
• In HCN, carbon has four valence electrons and forms a total of four bonds - one with hydrogen and three with nitrogen.

By grasping the concept of valence electrons, students can not only draw Lewis structures but also understand the bonding capabilities and tendencies of different elements.

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. It plays a critical role in determining a molecule’s physical and chemical properties, such as boiling point, reactivity, and polarity. The geometry is influenced by the number of bonds and lone pairs in a molecule as stated by the VSEPR theory (Valence Shell Electron Pair Repulsion).

For example, the molecular geometry of water is bent due to two bonding pairs and two lone pairs on the oxygen atom, causing the bonds to angle away from the lone pairs. In contrast, hydrogen chloride has a linear geometry since it only has one bond and three lone pairs on chlorine, which don't affect the single bond's orientation.

Bromine Chloride (BrCl) is also linear because it's a diatomic molecule with a single bond between the atoms, while hydrogen cyanide has a linear geometry because of the triple bond between carbon and nitrogen providing rigidity and leaving no lone electron pairs to repel each other. Understanding molecular geometry helps students predict molecule behavior and the outcome of chemical reactions.