Chemistry66 views·Updated Jun 12, 2026·3 pages

Comprehensive Review of Periodic Table Trends and Atomic Properties

Shreya Bedi@shreyabedi_oyaa

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Chemistry gets a lot more interesting when we start looking...

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# Chemistry

| POLYATOMIC IONS NAME | FORMULA | POLYATOMIC IONS NAME | FORMULA |
|---|---|---|---|
| Ammonium | NH₄⁺ | Hydroxide | OH⁻ |
| N

Polyatomic Ions and Ionic Compounds

Polyatomic ions are charged particles made of multiple atoms that act as a single unit. Some common ones include ammonium (NH₄⁺), hydroxide (OH⁻), nitrate (NO₃⁻), and sulfate (SO₄²⁻). You'll need to memorize these for your chemistry class!

When forming ionic compounds, we combine positive ions (cations) and negative ions (anions) to create neutral compounds. The key is to balance the charges. For example, when combining sodium (Na⁺) with hydroxide (OH⁻), we get NaOH because the charges balance out $+1 and -1$ .

For ions with multiple charges, we need to adjust the ratios. When magnesium (Mg²⁺) combines with acetate (C₂H₃O₂⁻), we need two acetate ions to balance magnesium's 2+ charge, giving us Mg(C₂H₃O₂)₂. The parentheses indicate that the entire polyatomic ion repeats.

💡 Quick Tip: When forming ionic compounds, cross the charges to find the subscripts. For example, Ca²⁺ and Cl⁻ form CaCl₂ because you need two Cl⁻ ions to balance the 2+ charge.

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Breaking Down Compounds and Naming Conventions

Breaking down compounds is like reverse-engineering a formula. For example, ZnO breaks down to Zn²⁺ + O²⁻, while more complex compounds like Fe₂(SO₄)₃ break down to 2Fe³⁺ + 3(SO₄²⁻). The key is ensuring the overall charge equals zero.

Compounds can be either ionic or covalent, and they follow different naming rules. Ionic compounds typically involve a metal and a nonmetal, like Na₂CO₃ (sodium carbonate). Covalent compounds usually form between nonmetals, like P₂O₅ (diphosphorus pentoxide).

For ionic compounds, name the cation first (usually a metal), then the anion. For covalent compounds, use prefixes $mono-, di-, tri-, tetra-, penta-, etc.$ to indicate the number of atoms. SiO₂ is silicon dioxide because there are two oxygen atoms.

📝 Remember: Transition metals often have Roman numerals in their names (like iron(II) or iron(III)) to indicate their charge, since these metals can form different charges in compounds.

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Writing Chemical Formulas

Converting between names and formulas is a critical chemistry skill. For covalent compounds like dinitrogen trioxide, the prefixes tell you exactly how many atoms to include—N₂O₃ has two nitrogen and three oxygen atoms.

For ionic compounds, you need to balance the charges. Lithium acetate combines Li⁺ with CH₃COO⁻ to form LiCH₃COO because their charges balance out. More complex examples include aluminum hydroxide, which combines Al³⁺ with three OH⁻ ions to form Al(OH)₃.

When metals can have multiple charges (like vanadium), the Roman numeral in the name tells you which charge to use. Vanadium(V) oxide means vanadium has a 5+ charge, so it would combine with oxygen (O²⁻) to form V₂O₅.

⚡ Master This: Create flashcards for common polyatomic ions and their charges. Being able to quickly recognize ions like PO₄³⁻ (phosphate) or SO₄²⁻ (sulfate) will save you tons of time when writing chemical formulas.

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Chemistry66 views·Updated Jun 12, 2026·3 pages

Comprehensive Review of Periodic Table Trends and Atomic Properties

Shreya Bedi@shreyabedi_oyaa

Add to Google sources

Chemistry gets a lot more interesting when we start looking at how atoms combine into compounds. This guide covers polyatomic ions, ionic compounds, and naming conventions that will help you ace your next chemistry test. Understanding these concepts is essential...

of 3

Polyatomic Ions and Ionic Compounds

💡 Quick Tip: When forming ionic compounds, cross the charges to find the subscripts. For example, Ca²⁺ and Cl⁻ form CaCl₂ because you need two Cl⁻ ions to balance the 2+ charge.

of 3

Breaking Down Compounds and Naming Conventions

📝 Remember: Transition metals often have Roman numerals in their names (like iron(II) or iron(III)) to indicate their charge, since these metals can form different charges in compounds.

of 3

Writing Chemical Formulas

⚡ Master This: Create flashcards for common polyatomic ions and their charges. Being able to quickly recognize ions like PO₄³⁻ (phosphate) or SO₄²⁻ (sulfate) will save you tons of time when writing chemical formulas.