Symbols & Charges
What is the charge on any Group 1 metal ion (e.g., sodium)?
1+
A word equation says "hydrogen gas reacts with nitrogen gas." Write the correct formula for each gas as it would appear in the equation.
H₂ and N₂
What two types of elements combine to form a covalent compound?
Two non metals
Write the correct formula for magnesium oxide, given Mg²⁺ and O²⁻.
MgO
Balance this equation: Mg + O₂ → MgO
2Mg + O₂ → 2MgO
Iron(III) is used in a compound name. What is the charge on this iron ion, and what is its symbol?
3+, Fe³⁺
True or False, and explain: "Chlorine" written alone in a word equation should be written as Cl in the chemical equation.
False — chlorine gas must be written Cl₂, since it exists as a diatomic molecule, not a lone atom
What must be present for a compound to be classified as ionic (name both components)?
A metal (or ammonium) and a nonmetal or polyatomic ion
Write the correct formula for aluminium oxide, given Al³⁺ and O²⁻.
Al₂O₃
Balance this equation: Al + O₂ → Al₂O₃
4Al + 3O₂ → 2Al₂O₃
Name the charge and formula of the nitrate ion.
1−, NO₃⁻
A reaction produces "oxygen gas" as a product. What formula must be written in the balanced equation, and why can't it just be O?
O₂ — oxygen never exists alone in nature as a single atom when it's a pure element
Classify iron(II) sulfide as ionic or covalent, and justify your answer using the identity of both elements.
Ionic — iron is a metal, sulfur is a nonmetal
Write the correct formula for potassium hydroxide, given K⁺ and OH⁻.
KOH
Balance this equation: N₂ + H₂ → NH₃
N₂ + 3H₂ → 2NH₃
A student sees "Copper(I) sulfate" in a reaction. Give the charge and symbol/formula for both the copper ion and the sulfate ion.
Cu⁺ (1+); SO₄²⁻ (2−)
Name all seven elements that exist as diatomic molecules when found alone in nature.
H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂
Dinitrogen tetroxide and calcium chloride are both named in a set of reactions. Classify each as ionic or covalent and explain the reasoning for both.
N₂O₄ is covalent (two nonmetals); CaCl₂ is ionic (metal + nonmetal)
Write the correct formula for ammonia, a covalent compound of one nitrogen atom and three hydrogen atoms.
NH₃
Write the full word equation "Zinc metal reacts with hydrochloric acid to produce zinc chloride and hydrogen gas" as a balanced chemical equation, starting from the unbalanced formula equation.
Zn + 2HCl → ZnCl₂ + H₂
An ionic compound has the formula Al(NO₃)₃. Using the "drop and swap" logic in reverse, what are the charges on the aluminium ion and the nitrate ion that must have combined to produce this formula?
Al³⁺ (3+) and NO₃⁻ (1−)
A word equation describes "bromine liquid reacting with potassium metal to produce potassium bromide." Identify which substance in this reaction is diatomic and write its correct formula.
Bromine is diatomic → Br₂ (potassium is not diatomic; it's a solid metal, written as K)
Hydrochloric acid is sometimes assumed to be ionic because it's an acid. Explain why it is actually classified as covalent/molecular.
HCl exists as discrete H–Cl molecules rather than a lattice of separate ions, even though it ionizes when dissolved in water, so it's classified as molecular/covalent
Write the correct formula for iron(III) oxide, given Fe³⁺ and O²⁻, showing your drop-and-swap and simplification steps.
Fe₂O₃ (swap charges to subscripts: Fe₂O₃, already fully simplified)
Write the full word equation "Silver oxide decomposes to form silver metal and oxygen gas" as a balanced chemical equation, starting all the way from identifying charges through to balancing.
2Ag₂O → 4Ag + O₂