Problem 2 - Chemistry: Principles and Reactions

Question

Name the following compounds. (a) \(\mathrm{HBrO}_{3}\) (b) KIO (c) \(\mathrm{NaClO}_{2}\) (d) \(\mathrm{NaBrO}_{4}\)

Step-by-Step Solution

Answer

Question: Name the following chemical compounds: (a) \(\mathrm{HBrO}_{3}\) (b) KIO (c) \(\mathrm{NaClO}_{2}\) (d) \(\mathrm{NaBrO}_{4}\) Answer: (a) Hydrogen bromate (b) Potassium iodate (c) Sodium chlorite (d) Sodium perbromate

Step 1: Identify the elements in each compound

(a) \(\mathrm{HBrO}_{3}\) has hydrogen (H), bromine (Br), and oxygen (O) elements. (b) KIO has potassium (K), iodine (I), and oxygen (O) elements. (c) \(\mathrm{NaClO}_{2}\) has sodium (Na), chlorine (Cl), and oxygen (O) elements. (d) \(\mathrm{NaBrO}_{4}\) has sodium (Na), bromine (Br), and oxygen (O) elements.

Step 2: Determine the type of compound - ionic or covalent

Ionic compounds are formed when a metal reacts with a non-metal. All compounds involving alkali metals (group 1 in the periodic table) or alkaline earth metals (group 2) are ionic. (a) \(\mathrm{HBrO}_{3}\) is not ionic because hydrogen is not a metal, so it is a covalent compound. (b) KIO is ionic because potassium (K) is an alkali metal (Group 1). (c) \(\mathrm{NaClO}_{2}\) is ionic because sodium (Na) is an alkali metal (Group 1). (d) \(\mathrm{NaBrO}_{4}\) is ionic because sodium (Na) is an alkali metal (Group 1).

Step 3: Name the compounds

Ionic compounds are named by writing the name of the metal first followed by the name of the non-metal(s), which often end in "ate" or "ite", depending on the number of oxygens. (a) \(\mathrm{HBrO}_{3}\): Hydrogen, bromine, and oxygen form a covalent compound, which is named as "bromate" (metal component), so the name is "hydrogen bromate". (b) KIO: In KIO, potassium is the metal part, and iodine with oxygen forms the "iodate" anion, so the compound name is "potassium iodate". (c) \(\mathrm{NaClO}_{2}\): In \(\mathrm{NaClO}_{2}\), sodium is the metal part, and chlorine with oxygen forms the "chlorite" anion, so the compound name is "sodium chlorite". (d) \(\mathrm{NaBrO}_{4}\): In \(\mathrm{NaBrO}_{4}\), sodium is the metal part, and bromine with oxygen forms the "perbromate" anion, so the compound name is "sodium perbromate".

Key Concepts

Covalent Compounds

Covalent compounds are formed when atoms share electrons to achieve a full outer shell. These compounds occur when two or more nonmetals bond together. Unlike ionic compounds, which involve a complete transfer of electrons from a metal to a non-metal, covalent bonds result from the sharing of electron pairs between atoms.
When naming covalent compounds, particularly those that are not acids, we traditionally use prefixes to indicate the number of each atom present in the molecule. Here are some common prefixes you might encounter:

• Mono- (for 1)
• Di- (for 2)
• Tri- (for 3)
• Tetra- (for 4)

In the compound \(\mathrm{HBrO}_{3}\), Br forms a polyatomic ion with oxygen called bromate. While hydrogen is sometimes (albeit complexly) considered a non-metal, it forms a covalent compound. Thus, it is called hydrogen bromate due to the presence of the bromate ion.

Ionic Compounds

Ionic compounds are formed through the complete transfer of electrons from one atom to another, leading to the generation of positively and negatively charged ions. This typically involves a metal and a non-metal. In ionic bonding, metals, found in groups 1 and 2 of the periodic table, lose electrons to become positively charged cations. In contrast, non-metals gain electrons to form negatively charged anions.
When it comes to naming ionic compounds, the metal's name (cation) appears first, followed by the base name of the anion, often ending with 'ide' if it is monoatomic or with 'ate' or 'ite' if it is part of a polyatomic ion. Here are examples from our exercise:

• Potassium iodate (KIO): Potassium (K) is a metal and iodine forms the iodate ion with oxygen.
• Sodium chlorite (\(\mathrm{NaClO}_{2}\)): Sodium (Na) is a metal and the polyatomic ion chlorite is formed from chlorine and oxygen.
• Sodium perbromate (\(\mathrm{NaBrO}_{4}\)): In this compound, sodium is the metal cation, and perbromate is the anion consisting of bromine and oxygen.

These distinct naming conventions help in identifying the components and properties of ionic substances.

Polyatomic Ions

Polyatomic ions are ions that consist of more than one atom. They are bonded together covalently but possess an overall charge, which may be positive or negative. These complex ions often consist of multiple non-metal atoms. The way these ions form bonds and appear in compounds is crucial to understand as they are commonly found in both covalent and ionic compounds.

• Bromate (\(\mathrm{BrO}_{3}^{-}\)): This is a common polyatomic ion where bromine covalently bonds with oxygen atoms, carrying an overall negative charge, and appears in hydrogen bromate.
• Iodate (\(\mathrm{IO}^{-}\)): Similar to bromate, iodate consists of iodine bonded with oxygen and is part of potassium iodate.
• Chlorite (\(\mathrm{ClO}_{2}^{-}\)): Found in sodium chlorite, this ion involves chlorine in covalent bonding with oxygen atoms.
• Perbromate (\(\mathrm{BrO}_{4}^{-}\)): This shares similar characteristics with bromate but with an additional oxygen atom, making it part of sodium perbromate.

Understanding polyatomic ions is essential for recognizing how they contribute to the structures and names of the compounds they form in various chemical scenarios.