Question

Write the formula for each of the following compounds: a. zinc chloride b. \(\operatorname{tin}(1 \mathrm{V})\) fluoride c. calcium nitride d. aluminum sulfide e. mercury(I) selenide f. silver iodide

Short answer

a. \( ZnCl_2 \) b. \( SnF_4 \) c. \( Ca_3N_2 \) d. \( Al_2S_3 \) e. \( Hg_2Se \) f. \( AgI \)

Step-by-step solution

a. Zinc Chloride

1. Identify ions: Zinc (Zn) has a charge of +2 and chloride (Cl) has a charge of -1. 2. Write formula: Since the charges are +2 and -1, we need two chloride ions to balance the charge of one zinc ion. The formula for zinc chloride is ZnCl2.

b. Tin(IV) Fluoride

1. Identify ions: Tin(IV) (Sn) has a charge of +4 and fluoride (F) has a charge of -1. 2. Write formula: Since the charges are +4 and -1, we need four fluoride ions to balance the charge of one tin ion. The formula for tin(IV) fluoride is SnF4.

c. Calcium Nitride

1. Identify ions: Calcium (Ca) has a charge of +2 and nitride (N) has a charge of -3. 2. Write formula: Since the charges are +2 and -3, we need three calcium ions to balance with two nitride ions. The formula for calcium nitride is Ca3N2.

d. Aluminum Sulfide

1. Identify ions: Aluminum (Al) has a charge of +3 and sulfide (S) has a charge of -2. 2. Write formula: Since the charges are +3 and -2, we need two aluminum ions to balance with three sulfide ions. The formula for aluminum sulfide is Al2S3.

e. Mercury(I) Selenide

1. Identify ions: Mercury(I) (Hg) has a charge of +1 and selenide (Se) has a charge of -2. 2. Write formula: Since the charges are +1 and -2, we need two mercury ions to balance the charge of one selenide ion. Note that mercury(I) is diatomic: Hg2^2+. The formula for mercury(I) selenide is Hg2Se.

f. Silver Iodide

1. Identify ions: Silver (Ag) has a charge of +1 and iodide (I) has a charge of -1. 2. Write formula: Since the charges are +1 and -1, we need one silver ion to balance the charge of one iodide ion. The formula for silver iodide is AgI.

Key concepts

Ionic Compounds

Ionic compounds are formed when positively charged ions, known as cations, and negatively charged ions, known as anions, come together. This typically occurs between metals and nonmetals. Metals, like zinc or tin, lose electrons and become positively charged. Nonmetals, like chlorine or fluorine, gain these electrons and become negatively charged. The attraction between these oppositely charged ions creates a strong bond. This bond forms a stable compound. For instance, in zinc chloride, zinc ions ( Zn^{2+} ) join with chloride ions ( Cl^{-} ) to create the ionic compound ZnCl_2 .

Ionic compounds often have high melting and boiling points due to the strong ionic bonds. They also conduct electricity when dissolved in water or melted due to the movement of ions. Understanding ionic compounds is crucial for writing accurate chemical formulas.

Charge Balancing

Charge balancing is a vital concept when writing chemical formulas for ionic compounds. The total positive charge from the cations must balance with the total negative charge from the anions. This creates a neutral compound overall. For example, in calcium nitride, three calcium ions ( Ca^{2+} ) provide a total positive charge of +6. This balances with the two nitride ions ( N^{3-} ) that give a total negative charge of -6. The formula becomes Ca_3N_2 .

To achieve charge balance, you might need multiple ions of one type to counter the charge of another. Always ensure that no net charge remains when you've written a chemical compound's formula. This balance ensures stability of the compound in its ionic lattice.

Chemical Nomenclature

Chemical nomenclature refers to the systematic way of naming chemical substances. It’s a crucial part of communicating in chemistry. For ionic compounds, the cation's name comes first, followed by the anion. If the cation is a transition metal, its charge is specified in Roman numerals in parentheses. This prevents confusion, especially for metals like tin or mercury, which can have multiple charges.

For instance, in tin(IV) fluoride, the "IV" indicates tin has a +4 charge. This distinguish it from other potential tin compounds with different charges. Similarly, in mercury(I) selenide, the (I) marks the unusual Hg_2^{2+} diatomic cation structure. Understanding these rules helps in writing and interpreting formulas accurately and avoids mixing up compounds with similar names but different chemical properties.

Transition Metals

Transition metals are unique elements found in the middle of the periodic table. They can form cations with various charges, unlike the consistent charges seen in main group metals. This variability comes from their d orbitals, which allow them to lose different numbers of electrons. For example, tin can form Sn^{2+} or Sn^{4+} ions, while mercury can form Hg^{2+} or Hg_2^{2+} .

This flexibility requires special attention in chemical nomenclature and in writing formulas. Transition metal names often include their charge in parentheses to clarify which ion is present. Understanding transition metals is crucial when dealing with ionic compounds, as they exhibit unique behaviors and bonding properties that differ significantly from other metals.