Question

Write the formula for each of the following compounds: a. chromium(VI) oxide b. disulfur dichloride c. nickel(II) fluoride d. potassium hydrogen phosphate e. aluminum nitride f. ammonia g. manganese(IV) sulfide h. sodium dichromate i. ammonium sulfite j. carbon tetraiodide

Short answer

a. Cr2O6 b. S2Cl2 c. NiF2 d. K2HPO4 e. AlN f. NH3 g. MnS2 h. Na2Cr2O7 i. (NH4)2SO3 j. CI4

Step-by-step solution

a. Chromium(VI) oxide

Chromium has a charge of +6 (since it's mentioned with (VI) roman numeral), and oxygen has a charge of -2. To write the formula for chromium(VI) oxide, we need to balance the charges. The balanced formula for chromium(VI) oxide is Cr2O6.

b. Disulfur dichloride

In disulfur dichloride, there are 2 sulfur atoms and 2 chlorine atoms. The formula for disulfur dichloride is S2Cl2.

c. Nickel(II) fluoride

Nickel has a charge of +2 (since it's mentioned with (II) roman numeral), and fluoride has a charge of -1. To write the formula for nickel(II) fluoride, we need to balance the charges. The balanced formula for nickel(II) fluoride is NiF2.

d. Potassium hydrogen phosphate

Potassium has a charge of +1, hydrogen has a charge of +1, and the polyatomic ion phosphate (PO4) has a charge of -3. To write the formula for potassium hydrogen phosphate, we need to balance the charges. The balanced formula for potassium hydrogen phosphate is K2HPO4.

e. Aluminum nitride

Aluminum has a charge of +3, and nitrogen has a charge of -3. To write the formula for aluminum nitride, we need to balance the charges. The balanced formula for aluminum nitride is AlN.

f. Ammonia

Ammonia consists of one nitrogen atom and three hydrogen atoms. The formula for ammonia is NH3.

g. Manganese(IV) sulfide

Manganese has a charge of +4 (since it's mentioned with the (IV) roman numeral) and sulfur has a charge of -2. To write the formula for manganese(IV) sulfide, we need to balance the charges. The balanced formula for manganese(IV) sulfide is MnS2.

h. Sodium dichromate

Sodium has a charge of +1 and the polyatomic ion dichromate (Cr2O7) has a charge of -2. To write the formula for sodium dichromate, we need to balance the charges. The balanced formula for sodium dichromate is Na2Cr2O7.

i. Ammonium sulfite

The polyatomic ion ammonium (NH4) has a charge of +1, and the polyatomic ion sulfite (SO3) has a charge of -2. To write the formula for ammonium sulfite, we need to balance the charges. The balanced formula for ammonium sulfite is (NH4)2SO3.

j. Carbon tetraiodide

Carbon tetraiodide consists of one carbon atom and four iodine atoms. The formula for carbon tetraiodide is CI4.

Key concepts

Ionic Compounds

Ionic compounds are chemical compounds composed of ions held together by electrostatic forces termed ionic bonding. They consist of positive ions, called cations, and negative ions, called anions. When these ions bond together, they form a neutral compound, as the charges must balance each other.
For example,

• Chromium(VI) oxide is an ionic compound because it is made up of chromium ions ( ext{Cr}^{6+}) and oxide ions ( ext{O}^{2-}). The charges of the ions must balance, hence the formula is ext{Cr}_2 ext{O}_6.
• Nickel(II) fluoride consists of nickel ions ( ext{Ni}^{2+}) and fluoride ions ( ext{F}^{-}). Here, two fluoride ions are needed to balance the charge of one nickel ion, resulting in the formula ext{NiF}_2.

Understanding how charges balance is crucial in writing correct formulas for ionic compounds, ensuring the compound has no overall charge.

Naming Compounds

Naming compounds is an essential skill in chemistry, helping to communicate the structure and composition of a compound. Rules in chemical nomenclature dictate how different types of compounds get their names.

• Ionic compounds typically take the name of the cation first, and the anion second. For example, potassium hydrogen phosphate consists of potassium ions and hydrogen phosphate ions, resulting in the name.
• For covalent compounds like disulfur dichloride, prefixes (di-, tri-, tetra-, etc.) indicate the number of atoms. "Di-" means two, and "tetra-" means four, aiding in the correct depiction of S ext{Cl}_2 or CI ext{I}_4.

These naming conventions ensure clarity and accuracy in communication across scientific disciplines.

Polyatomic Ions

Polyatomic ions are ions composed of two or more atoms covalently bonded together, which act as a single ion with a net charge. Recognizing polyatomic ions is key to writing chemical formulas correctly.

• In ammonium sulfite ( ext{(NH}_4)_2 ext{SO}_3), ammonium ( ext{NH}_4^+) and sulfite ( ext{SO}_3^{2-}) are polyatomic ions. Balancing their charges leads to this specific formula.
• Similarly, sodium dichromate ( ext{Na}_2 ext{Cr}_2 ext{O}_7) involves the polyatomic dichromate ion ( ext{Cr}_2 ext{O}_7^{2-}). Knowing the charges helps in deducing the formula.

An understanding of common polyatomic ions can simplify the process of determining the chemical formula of a compound.

Chemical Nomenclature

Chemical nomenclature is a systematic way of naming substances, critical to scientific communication. It establishes universally accepted language for chemists worldwide, simplifying the organization and classification of chemicals.

• Elements and ions with specific charges often use Roman numerals, such as chromium(VI) or nickel(II), indicating their oxidation state.
• The systematic names for polyatomic ions, like phosphate or dichromate, follow established conventions aiding in memory retention and clarity.

Using proper chemical nomenclature is essential for understanding chemical reactions, safety data, and regulatory information, making it a foundational topic for chemistry students.