Question

Write the correct formula for the following compounds: a. barium hydroxide b. sodium sulfate c. iron(II) nitrate d. zinc phosphate e. iron(III) carbonate

Short answer

a. Ba(OH)₂, b. Na₂SO₄, c. Fe(NO₃)₂, d. Zn₃(PO₄)₂, e. Fe₂(CO₃)₃

Step-by-step solution

Identify the elements and radicals

Determine the chemical symbols for each element and any polyatomic ions. For example, for barium hydroxide, barium is Ba and hydroxide is OH.

Determine valencies or charges

Determine the common valencies or ionic charges of each part of the compound. For instance, barium (Ba) has a valency of +2, and hydroxide (OH) has a valency of -1.

Balance the charges

Balance the charges by ensuring the total positive charge equals the total negative charge. So, for barium hydroxide (Ba(OH)₂), two hydroxide ions are needed to balance one barium ion.

Write the chemical formulas

Using the balanced charges, write the correct chemical formula for each compound. Continue this process for each given compound.

Key concepts

Understanding Chemical Symbols

Chemical symbols are abbreviations used to represent chemical elements. These symbols are usually derived from the Latin name of the element. For example, the symbol for sodium is Na, which comes from its Latin name 'Natrium'.
Each chemical symbol consists of one or two letters. The first letter is always capitalized, and if there is a second letter, it is written in lowercase. For example, the chemical symbol for iron is Fe, derived from 'Ferrum'.
Knowing these symbols is crucial because they provide a universal shorthand for identifying elements in compounds and chemical reactions.

Why Ionic Charges Matter

Ionic charges indicate the electrical charge of an ion formed when atoms gain or lose electrons. These charges are essential in forming compounds because they determine how ions interact and bond. For example, a sodium ion (Na⁺) has a +1 charge because it loses one electron, while a chloride ion (Cl⁻) has a -1 charge because it gains one electron.

• Cations: Positively charged ions (e.g., Na⁺, Ca²⁺).
• Anions: Negatively charged ions (e.g., Cl⁻, SO₄²⁻).

Balancing these ionic charges is critical when writing chemical formulas. Take barium hydroxide (Ba(OH)₂); barium has a +2 charge, and hydroxide has a -1 charge. Two hydroxide ions are required to balance the charge of one barium ion.
Knowing the common charges of elements and polyatomic ions helps in predicting and writing the correct chemical formulas.

Understanding Valency

Valency is the combining power of an element, especially measured by the number of hydrogen atoms it can displace or combine with. It indicates how many electrons an atom will gain, lose, or share when it forms chemical bonds. For example:

• Monovalent: One valency (e.g., Na⁺, Cl⁻).
• Divalent: Two valencies (e.g., Mg²⁺, O²⁻).
• Trivalent: Three valencies (e.g., Al³⁺, N³⁻).

Understanding valency simplifies predicting how elements will combine to form compounds. For instance, iron can have multiple valencies. Iron (II) indicates a valency of +2 (Fe²⁺), while iron (III) indicates a valency of +3 (Fe³⁺). This is important when distinguishing between compounds like iron(II) sulfate (FeSO₄) and iron(III) sulfate (Fe₂(SO₄)₃).
In summary, knowing the valency allows you to determine the proportions in which elements will combine, making it easier to write correct chemical formulas.