Question

Write the formula for each molecule. \(\begin{array}{ll}{\text { a. silicon dioxide }} & {\text { c. chlorine trifluoride }} \\ {\text { b. bromous acid }} & {\text { d. hydrobromic acid }}\end{array}\)

Short answer

The chemical formulas for the given molecules are as follows: a. Silicon dioxide: SiO\(_2\) b. Bromous acid: HBrO\(_2\) c. Chlorine trifluoride: ClF\(_3\) d. Hydrobromic acid: HBr

Step-by-step solution

a. Silicon dioxide

Silicon dioxide is composed of two elements: silicon (Si) and oxygen (O). Silicon has a valence of +4, and oxygen has a valence of -2. To determine the proper ratio of silicon and oxygen in the compound, we need to find the lowest common multiple of their charges. In this case, since the charges are +4 and -2, the lowest common multiple is 4. Therefore, we will need 1 silicon atom and 2 oxygen atoms to balance the charges. The chemical formula for silicon dioxide is thus SiO\(_2\).

b. Bromous acid

Bromous acid is composed of hydrogen (H), bromine (Br), and oxygen (O). In this case, bromine is in the form of the bromite ion (BrO\(_2\)\(^{-}\)). Hydrogen has a valence of +1, and the bromite ion has a valence of -1. To balance the charges, we need 1 hydrogen atom and 1 bromite ion. The chemical formula for bromous acid is HBrO\(_2\).

c. Chlorine trifluoride

Chlorine trifluoride is composed of chlorine (Cl) and fluorine (F). Chlorine has a valence of +3 (as it will form 3 bonds with fluorine) and fluorine has a valence of -1. To balance the charges, we need 1 chlorine atom and 3 fluorine atoms. The chemical formula for chlorine trifluoride is ClF\(_3\).

d. Hydrobromic acid

Hydrobromic acid is composed of hydrogen (H) and bromine (Br). Hydrogen has a valence of +1 and bromine forms a monatomic anion with a valence of -1. To balance the charges, we need 1 hydrogen atom and 1 bromine atom. The chemical formula for hydrobromic acid is HBr.

Key concepts

Valence Electrons

Understanding valence electrons is essential when it comes to writing chemical formulas. These electrons are located in the outermost shell of an atom and are responsible for the atom's ability to form bonds with other atoms. In essence, valence electrons are the atom's 'handshake' – they determine how atoms interact and connect with one another.

For instance, in the exercise provided, when determining the formula for silicon dioxide, we consider that silicon has four valence electrons and seeks to share them with oxygen atoms, which each need two electrons to complete their valence shell. By sharing valence electrons, atoms reach a more stable state, often resulting in the rule of 'octet'—an atom possessing eight electrons in its outer shell. With this concept, students can predict the bonding patterns of elements and the ratios in which they'll combine.

Chemical Bonds

Chemical bonds are the forces holding atoms together in molecules. They are formed by the interactions of valence electrons between atoms. There are three primary types of bonds: ionic, covalent, and metallic. Ionic bonds are formed between metals and nonmetals and involve the transfer of electrons. Covalent bonds occur when two nonmetals share electrons. Metallic bonds are unique to metals, where electrons are free to move around.

For example, the creation of bromous acid, as described in step 2, involves the formation of a covalent bond between the hydrogen atom and the bromite ion. Each wants to achieve a stable electron configuration, which is achieved through sharing their valence electrons. By keeping this process in mind, students can more accurately predict the resulting compound structures and their chemical formulas.

Chemical Nomenclature

Chemical nomenclature refers to the system of names for chemical compounds. It can seem daunting at first, but it's akin to learning the vocabulary of chemistry. The naming of a compound provides a lot of information about its structure, such as the elements involved and their ratios.

Consider hydrobromic acid, from step 4. Its name tells us hydrogen and bromine are present in a one-to-one ratio, resulting in the formula HBr. The prefix 'hydro-' indicates that hydrogen is bonded to a nonmetal, while 'bromic' derives from the name of the nonmetal, bromine. This systematic approach to naming ensures that scientists across the globe can communicate with consistency and clarity about chemical compounds.