Grade 10 · Science · Chemistry

10th grade Write formulas for ionic compounds worksheet

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Write formulas for ionic compounds

Grade 10 Science Worksheet

NameDate

Circle the best answer, or write your answer on the line.

A student writes a formula with 3 aluminum ions (+3 each) and 2 oxide ions (−2 each). What is its net charge, Ari?
A student writes a formula with 3 calcium ions (+2 each) and 2 chloride ions (−1 each). What is its net charge, Esme?
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Balancing charges with the least common multiple (worked examples). Columns: compound, cation charge, anion charge, LCM, ions in the formula. MgO, +2, −2, 2, 1 Mg²⁺, 1 O²⁻; CaCl₂, +2, −1, 2, 1 Ca²⁺, 2 Cl⁻; Al₂O₃, +3, −2, 6, 2 Al³⁺, 3 O²⁻.
3.
Using the table, why does Al₂O₃ have 2 aluminum ions, Jun?
- 3 ÷ 2 = 2
- 6 ÷ 2 = 2
- 6 ÷ 3 = 2
4.
Using the table, why is MgO written with one of each ion, Kira?
- +2 and −2 already balance
- Magnesium has just one shell left
- Oxygen is lighter
5.
Using the table, what is the total positive charge in one Al₂O₃ unit, Luz?
- +3
- +6
- +5
6.
What is the formula for aluminum oxide, Noah?
- Al₂O₃
- Al₃O₂
- AlO
7.
Which is written first in an ionic formula, Pia?
- The lighter ion
- The nonmetal
- The metal
8.
What does the formula NaCl tell you about table salt, Ren?
- Na⁺ and Cl⁻ are in a 1 : 1 ratio
- It has one single ion
- It is a molecule of two atoms
9.
What is a formula unit, Tala?
- The smallest ratio of ions
- A single atom
- One shared molecule of the salt
10.
How is CaCl₂ different from H₂O, Zee?
- H₂O is made of separate ions
- CaCl₂ is a lattice of ions
- CaCl₂ is a gas

Write formulas for ionic compounds. Every version has 10 questions, and the answer key prints on the second page.

I can give ion charges from the group: +1, +2, +3, −2, −1.
I can write formulas whose charges add to zero, using the least common multiple (Al₂O₃).
I can check a written formula's net charge and spot formulas that don't balance or aren't in lowest terms.
I can treat carbonate (CO₃²⁻) as one ion, as in chalk (CaCO₃).

Standard: none (TX)

ion: An atom or group with a charge

formula unit: The smallest whole-number ratio of ions in an ionic compound

least common multiple (LCM): The smallest number both charges divide into

polyatomic ion: A group of atoms with one shared charge, like CO₃²⁻

net charge: The sum of all the charges in a formula

Your child turned the charges upside down. Anions needed = cations × cation charge ÷ anion charge.

Your child added every charge as positive. Anion charges are negative, so subtract them: net = cations × charge − anions × charge.

Your child turned the ratio upside down. Use the formula's ratio: anions per cation = x ÷ y.

What is the most common mistake with write formulas for ionic compounds?

Your child turned the charges upside down. Anions needed = cations × cation charge ÷ anion charge.

Are these 10th grade science worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

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