Final review · all units
Chemistry Final — Study Guide
Work through each part, study the picture, then try the practice — tap Show answer to check yourself. The examples here are new on purpose: if you understand the idea, you can answer any version on the test.
How to use this guide
- Read each part, then look at its diagram.
- Try the Practice questions and tap Show answer to check.
- The last part — Chemical Reactions — is not on the final. It is a preview of what comes next.
Key Words in Your Language
These science words look alike in English, Spanish, Portuguese, and French. Use them as you read.
Part A — How Atoms Become Ions
Atoms are most stable with a full outer shell of 8 valence electrons (the octet rule). Valence electrons live in the outermost energy level.
Metals have few valence electrons, so they lose them and become positive ions (cations). Nonmetals are almost full, so they gain electrons and become negative ions (anions).
Practice
Magnesium (Mg) has 2 valence electrons. Will it lose or gain electrons, and what ion does it form?
Show answer
Loses 2 electrons → Mg²⁺ (a cation).
Sort by the ion they form — cation (+) or anion (−): Potassium (K), Oxygen (O), Calcium (Ca), Fluorine (F).
Show answer
Cations: K, Ca. Anions: O, F.
Finish the idea: atoms gain or lose electrons to reach ____ valence electrons and become ____.
Show answer
8; stable.
Part B — Ionic Bonds
An ionic bond forms between a metal and a nonmetal. Electrons are transferred from the metal to the nonmetal. The opposite charges (+ and −) attract, and the ions stack into a repeating 3-D crystal lattice.
Practice
Will Potassium (K) and Bromine (Br) form an ionic bond? Explain in one sentence.
Show answer
Yes — K is a metal and Br is a nonmetal, so K transfers an electron to Br.
How is an ionic bond different from a metallic bond, in terms of the electrons?
Show answer
Ionic: electrons are transferred to the nonmetal. Metallic: electrons are delocalized (a shared sea).
The repeating 3-D structure of an ionic compound is called a ____.
Show answer
crystal lattice.
Part C — Metallic Bonds & Why Metals Behave the Way They Do
In a metal, positive ions sit in a sea of delocalized electrons (free to move). This electron sea explains three properties at once.
Conductivity: free electrons carry charge. Malleability: the ions slide past each other while the sea holds them together, so the metal bends instead of breaking. Luster: the electron sea reflects light, so metals look shiny.
Compare all three bond types by what the electrons do: ionic = transferred, covalent = shared, metallic = delocalized.
Practice
Match each everyday fact to a property (conductivity / malleability / luster): (a) a copper charging cable, (b) gold hammered into thin leaf, (c) a clean aluminum pan looks shiny.
Show answer
a = conductivity, b = malleability, c = luster.
A metal spoon bends when pressed, but a salt crystal shatters when hit. Use the electron sea to explain why the metal bends.
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The metal ions slide past each other while the electron sea keeps them bonded, so it changes shape instead of breaking.
Match each bond type to its electrons: ionic = ____, covalent = ____, metallic = ____.
Show answer
transferred / shared / delocalized.
Part D — Naming Ionic Compounds & Polyatomic Ions
Name = metal name + nonmetal ending in –ide (sodium + chlorine → sodium chloride). To get the formula, criss-cross the charges so the compound is neutral.
Polyatomic ions are groups that act as one unit with one charge — keep the whole name (nitrate stays nitrate). Use parentheses when you need more than one.
Practice
Name the compound MgCl₂.
Show answer
magnesium chloride.
Write the formula for potassium sulfide.
Show answer
K₂S.
Calcium is Ca²⁺ and nitrogen is N³⁻. Use criss-cross to write the formula.
Show answer
Ca₃N₂.
Name K₂SO₄ (SO₄²⁻ = sulfate).
Show answer
potassium sulfate.
Part E — Covalent Bonds, Polarity & Electronegativity
A covalent bond forms when two nonmetals share electrons. A molecule is two or more atoms covalently bonded.
Electronegativity (EN) is how strongly an atom pulls the shared electrons. Equal pull → nonpolar. Unequal pull → polar. The bigger the difference (ΔEN), the more polar — and a very large ΔEN makes the bond ionic.
Practice
Is the bond in O₂ (two oxygen atoms) polar or nonpolar? Why?
Show answer
Nonpolar — the two identical atoms pull equally.
Rank these bonds from least to most polar: F–F, H–Cl, Na–Cl.
Show answer
F–F (nonpolar) < H–Cl (polar) < Na–Cl (ionic).
A very large electronegativity difference makes a bond ____ instead of covalent.
Show answer
ionic.
In your own words, what is a molecule?
Show answer
Two or more atoms held together by covalent (shared) bonds.
Part F — Molecular Shapes (VSEPR)
VSEPR predicts a molecule's 3-D shape. Just count how many atoms surround the central atom.
Practice
Methane (CH₄) has 4 atoms around the central carbon. What is its shape?
Show answer
tetrahedral.
Carbon dioxide (CO₂) has 2 atoms around the central carbon. What is its shape?
Show answer
linear.
A molecule has 6 atoms around the central atom. Name the shape.
Show answer
octahedral.
Part G — Naming Covalent Compounds (Greek Prefixes)
For two nonmetals, use a prefix to show the number of each atom. Skip 'mono' on the first element. The second element ends in –ide.
Practice
Name SF₆.
Show answer
sulfur hexafluoride.
Name CCl₄.
Show answer
carbon tetrachloride.
Write the formula for dinitrogen trioxide.
Show answer
N₂O₃.
Part H — Lewis Structures: Polar or Nonpolar?
A Lewis structure shows the central atom, the bonds, and the lone pairs. To decide polarity, look at the shape: if it is symmetric the pulls cancel → nonpolar; if it is asymmetric the pulls add up → polar.
Practice
CO₂ is symmetric and H₂O is bent/asymmetric. Which one is polar?
Show answer
H₂O.
If a molecule is symmetric and the pulls cancel, is it polar or nonpolar?
Show answer
nonpolar.
Where this goes next — Chemical Reactions (not on the final)
This part is not on your final — it is a preview of where chemistry goes next.
When atoms rearrange, a chemical reaction happens. Reactants (start) are on the left; products (end) are on the right. Signs of a reaction: a color change, bubbles of gas, a precipitate (a solid that forms in a liquid), or a change in energy/temperature. The main types are synthesis, decomposition, single replacement, double replacement, and combustion.