Chemistry Science - Term 3 - 2025

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What do the rows (periods) on the periodic table show?

The number of electron shells.

What do the columns (groups) on the periodic table show?

The number of valence electrons.

What does the atomic number equal?

Number of protons (and electrons in a neutral atom).

How do you calculate the number of neutrons?

Mass number – atomic number.

What are Group 17 elements called, and how reactive are they?

Halogens, very reactive.

What are Group 18 elements called, and how reactive are they?

Noble gases, non

What is an isotope?

Atoms of the same element with same protons but different neutrons.

What changes in isotopes?

Mass number.

What is an ion?

An atom that has gained or lost electrons.

What is a cation?

A positively charged ion (lost electrons).

What is an anion?

A negatively charged ion (gained electrons).

Why do atoms form ions?

To achieve a full outer shell (stability).

Properties of metals.

Malleable/ductile, lustrous, good conductors.

What do metals form

Cations (+).

List three properties of non-metals.

dull, insulators, brittle when solid

Do non-metals form cations or anions?

anions

What type of ions form in ionic bonding?

Cations and anions.

How are electrons involved in ionic bonding?

Transferred.

How are electrons involved in covalent bonding?

Shared.

How are electrons involved in metallic bonding?

Delocalised in a sea of electrons.

What type of elements form ionic bonds?

Metals + non

What type of elements form covalent bonds?

2 non-metals

What type of elements form metallic bonds?

Metals.

Which bonding has a high melting point and dissolves in water?

Ionic.

Which bonding has a low melting point and dissolves in non-polar solvents?

Covalent bonds

Which bonding conducts electricity well in solid form?

Metallic.

What are diatomic molecules?

Pairs of the same atom bonded together.

Name the 7 diatomic molecules.

H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂.

What is a polyatomic ion?

A stable group of 3+ atoms bonded together with a charge.

How are ionic compounds named?

Metal first, non-metal ends in -ide

How are covalent compounds named?

Prefixes for number, second element ends in –ide.

What is the general reaction of a metal + acid?

Salt + hydrogen.

What is the reaction of base/hydroxide + acid?

Salt + water.

What is the reaction of carbonate + acid?

Salt + water + carbon dioxide.

What is the reaction of ammonia + acid?

Ammonium salt.

Synthesis reaction

A + B → AB.

What is a decomposition reaction?

AB → A + B.

What is a single displacement reaction?

A + BC → AC + B.

What is a double displacement reaction?

AB + CD → AD + BC.

Combustion reaction

CxHy + O₂ → CO₂ + H₂O.

Signs of a chemical reaction

Gas produced, colour change, solid formed, energy released.

What does the Law of Conservation of Mass state?

Mass is neither created nor destroyed.

What ion do acids release in water?

H⁺.

What ion do bases release in water?

OH⁻.

What pH range do acids have?

<7

What pH range do bases have?

7.

Properties of acids

Sour taste, reactive, corrosive, conduct electricity.

List two properties of bases.

Bitter taste, feel soapy, clean grease, conduct electricity.

What is a strong acid?

Fully dissociates in water.

What is a weak acid?

Partially dissociates in water.

What is a concentrated acid?

High amount of solute per litre.

What colour does red litmus paper turn in base?

Blue.

What colour does blue litmus paper turn in acid?

Red.

What happens to litmus paper in a neutral solution?

No colour change.

What is an exothermic reaction?

Releases energy as heat/light.

What is an endothermic reaction?

Absorbs energy, feels cooler.

What is half-life

the time it takes for half of a quantity of a substance to be used up or decay into a different substance

Does each isotope have the same half-life?

No, it varys

What stops alpha radiation?

Paper.

What stops beta radiation?

Aluminium.

What can gamma radiation pass through?

Almost everything.