Year 10 Chemistry (i'm cooked)

What is the structure of an atom?

• Nucleus at the centre

  • Contains protons (positive charge)

  • Contains neutrons (no charge)

  • Dense and small compared to the whole atom

• Electrons orbit the nucleus

  • Negative charge

  • Found in electron shells

  • Very light compared to protons and neutrons

• Most of the atom is empty space

• Overall atom is electrically neutral (same number of protons and electrons)

• Atomic number = number of protons

• Mass number = protons + neutrons

What is the electron shell configuration?

2, 8, 8, 18

What is an element?

An element is a pure substance made of only one type of atom. It cannot be broken down into a simpler substance by chemical means.

How to calculate protons, neutrons, and electrons?

• Protons = Atomic Number

• Electrons = Protons (if neutral atom)

• Electrons = Protons ± charge (for ions)

• Neutrons = Mass Number − Atomic Number

What is the periodic table arranged by?

Increasing atomic number (number of protons).

What are groups in the periodic table?

Vertical columns (numbered 1 to 18).

What do elements in the same group have in common?

The same number of valence electrons and similar chemical properties.

What are valence electrons?

Electrons in the outermost shell of an atom.

Why are valence electrons important?

They determine how an atom reacts and bonds with other atoms.

What are periods in the periodic table?

Horizontal rows (numbered 1 to 7).

What do elements in the same period have in common?

The same number of occupied electron shells.

Where are the transition metals located?

In the centre of the table — groups 3 to 12.

What are some properties of transition metals?

Good conductors, high melting points, form coloured compounds, and have variable oxidation states.

What are the names of some important groups?

• Group 1: Alkali metals

• Group 2: Alkaline earth metals

• Group 17: Halogens

• Group 18: Noble gases

What formula is used to calculate the maximum number of electrons in an electron shell?

2n², where n is the shell number.

E.g. 2×3² = 18

Define valency

The number of electrons in an atom’s outer shell that an atom can lose, gain, or share to form bonds.

How is an element’s group related to its valency?

For main groups, the valency usually equals the group number (for Groups 1–2 and 13–18).

What group do elements with 8 valence electrons usually belong to?

Group 18 (noble gases).

Why don’t transition metals follow the valency-group rule clearly?

Because they have variable valency and can lose different numbers of electrons.

If an element has 3 occupied electron shells, what period is it in?

Period 3.

Does the period number tell you anything about valence electrons?

No, it only shows the number of electron shells occupied.

What is electron configuration?

The arrangement of electrons in an atom’s shells, listed by the number of electrons in each shell.

How do you predict the charge of an ion?

By looking at how many electrons an atom gains or loses to have a full outer shell.

• Metals form cations

• Non-metals form annions

What charge does an atom with 1 valence electron usually form?

+1 (loses 1 electron).

It loses that 1 electron to get a full outer shell underneath, resulting in a positive charge.

What charge does an atom with 7 valence electrons usually form?

-1 (gains 1 electron).

What charge do noble gases usually form?

0 (they are stable and don’t usually form ions).

How do transition metals differ in ion charges?

They can have variable charges, so you often need to check the specific element.

What does diatomic mean?

It means an element naturally forms molecules with two atoms, like H₂.

Why is hydrogen diatomic?

• A single hydrogen atom is unstable with only one electron

• Two hydrogen atoms share electrons by forming a single covalent bond (H₂)

• Makes both atoms stable with a full outer shell.

• Only as a pure element or in covalent bonding with itself

Which elements are diatomic?

H₂, N₂, F₂, O₂ I₂, Cl₂, Br₂ — "Have No Fear Of Ice Cold Beer".

Metals vs Non Metals

Feature	Metals	Non-metals
Location on PT	Left and middle	Right side (plus H)
Appearance	Shiny (lustrous)	Dull or colourful
Conductivity	Good conductors (heat + electricity)	Poor conductors
Malleability	Malleable and ductile	Brittle
State at room temp	Mostly solid (except Hg)	Solid, liquid, or gas
Example elements	Na, Fe, Cu, Mg, Al	O, N, Cl, S, C, H

How do ions form?

Ions are formed when an atom gains or loses electrons, resulting in a net electrical charge.

Cation vs Anion

Cation: Positive

Anion: Negative

What are the properties of alkali metals (Group 1)?

• Soft, shiny metals

• Very reactive (especially with water)

• Low melting points

• Stored in oil

• Reactivity increases down the group

What are the properties of alkaline earth metals (Group 2)?

• Harder than alkali metals

• Reactive (but less than Group 1)

• Burn with colourful flames

• Form basic (alkaline) oxides

What are the properties of halogens (Group 17)?

• Very reactive non-metals

• Poisonous

• Coloured

• Exist as diatomic molecules (e.g. Cl₂)

• Reactivity decreases down the group

What are the properties of noble gases (Group 18)?

• Very unreactive

• Colourless gases

• Full outer electron shells

• Low boiling points

• Used in lights and signs

Describe the increasing reactivity of metals down Group 1 & 2.

• Reactivity increases as you go down the group

• Outer electrons are further from the nucleus

• Weaker attraction between nucleus and outer electrons

• Electrons are easier to lose, so reactions happen more easily

• Group 1 metals react more strongly with water than Group 2 metals

What is an isotope?

• Atoms of the same element (same number of protons)

• Different number of neutrons

• Different mass number but same chemical properties

Why do elements form bonds?

The atoms of elements that are unstable are able to fill the outer shells and become stable.

What are the three types of bonding?

1. Ionic Bonding

   • Occurs between metal and non-metal atoms

2. Covalent Bonding

   • Occurs between non-metals only

3. Metallic Bonding

   • Occurs between metal atoms only

All bonds involve electrons and all bonding involve changes to the number of electrons in the outer shells of atoms.

Explain delocalised electrons

• In metals, the metal atoms lose their outer electrons to form metal ions

• The electrons from all the metal atoms form a “sea” of electrons that can flow around the metal

• Delocalised means the electrons are not fixed in one place

• electrons hold metal ions in place in a lattice

What are the metallic properties?

• Conduct heat

• Conduct electricity

• Generally high melting and boiling points

• Strong (not brittle)

• Malleable (can be hammered or pressed out of a shape without breaking)

• Ductile (able to be drawn into a wire)

• Metallic lustre (shiny)

• Opaque (reflect light)

Why does metal have a high melting and boiling point?

• The strength of the electrostatic force of attraction (metallic bond)

• The bond is very strong and requires large amounts of thermal energy to break

What is an ionic bond?

A bond formed by the transfer of electrons from one atom to another.

• Metal and non-metal atoms

• Electrons are transferred from each metal atom to each non-metal ions

• Metal and non-metal atoms form ions with completely full outer shells and become stable

What happens to the metal atom in an ionic bond?

It loses electrons and becomes a positively charged ion (cation).

What happens to the non-metal atom in an ionic bond?

It gains electrons and becomes a negatively charged ion (anion).

What causes the ionic bond to hold the atoms together?

The positive and negative ions are strongly attracted to each other. This electrostatic attraction is called ionic bonding.

What are compounds that contain ions called?

• Ionic compounds

• Usually formed by a reaction between a metal and non-metal

What are bonds?

Bonds are forces that hold atoms together.
Types:

• Covalent – atoms share electrons (non-metals).

• Ionic – atoms transfer electrons (metal + non-metal).

• Metallic – free-moving electrons shared among metal atoms.

What are the properties of ionic bonds?

• High melting & boiling points

• Conduct electricity when molten or in solution

• Usually solid at room temperature

• Form crystals

• Soluble in water

• Brittle

Describe the structure of covalent bonds

• Covalent bonds have a structure where atoms share electrons to fill their outer shell.

• The shared electrons join the atoms together.

What is a covalent network substance?

• A substance with a giant lattice of atoms bonded by strong covalent bonds.

• high melting point

• hard and non-conductive (e.g. diamond)

What are covalent molecular solids

• Small molecules held together by weak intermolecular forces (forces between, not within)

  • E.g. Hydrogen bonds

• low melting points

• non-conductive

• E.g. bonds between carbon dioxide and/or water molecules

Covalent network vs covalent molecular substances

Feature	Covalent Network	Covalent Molecular
Structure	Giant lattice of atoms bonded by strong covalent bonds	Small, separate molecules held together by weak forces
Bonding	Strong covalent bonds throughout the whole structure	Strong covalent bonds within molecules, but weak intermolecular forces between them
Melting & Boiling Points	Very high (due to strong bonds throughout)	Low (due to weak forces between

How to write ionic formula

• Formula of a compound uses chemical symbols and numbers to show the ratio of atoms of each element present

1. Write down the name for each element

   • The metal is always written first

2. Calculate the charge for each type of ion

3. Balance the number of ions so that the positive and negative charges are balanced and equal zero. This gives the ratio of ions.

4. Use the ratio to write down the formula of the ionic compound

Describe the formation of ionic compounds

• Millions and millions of ions are packed together in a regular cubic arrangement, joined by ionic bonds.

• Ionic compounds form a giant 3D structure called an ionic lattice

• The ionic lattice will continue to build this way until there are no more ions left to add

• The structure of the ionic lattice affects the properties of the ionic compound

Describe covalent bond properties

• Low melting and boiling points

• Usually gases or liquids at room temperature

• Poor electrical conductivity

• Insoluble or slightly soluble in water

• Form between non-metal atoms

• Share electrons between atoms

How to name covalent substances?

1. Elements are written in order of left to right on the periodic table

2. The second element has the suffix “-ide”

3. Elements are given a prefix to state the number of atoms (except one atom of the first element)

How do you write the formula for a covalent substance?

Use the molecular formula showing the number of atoms of each element in one molecule.

What is the law of conservation of mass?

Mass cannot be created or destroyed in a chemical reaction.

How to name metallic bonds?

• Name the metal (cation) first — just the element name.

• Name the non-metal (anion) second — use the root of the element + -ide ending.

Examples:

• NaCl → Sodium chloride

• MgO → Magnesium oxide

• CaF₂ → Calcium fluoride

What is a decomposition reaction?

When a single reactant breaks apart to form several products, the reactant is said to decompose.

• XY → X + Y

An example is the decomposition of carbonic acid into H2O and CO2.

• H2CO3 (aq) → H2O (l) + CO2 (g)

Describe a precipitation reaction

• Sometimes two clear solutions are mixed together and go cloudy

• This means that an insoluble substance has been created which comes out of solution and forms a solid

• This is called a precipitate

Acid-Metal Reaction

• Word: Acid + Metal → Salt + Hydrogen gas

• Example: Hydrochloric acid + Zinc → Zinc chloride + Hydrogen gas

• Formula: 2HCl + Zn → ZnCl₂ + H₂

How to name salt?

• Name the metal (cation) first.

• Name the acid’s negative ion (anion) second.

• If acid ends with -ic, salt ends with -ate (e.g., sulfuric acid → sulfate).

• If acid ends with -ous, salt ends with -ite (e.g., sulfurous acid → sulfite).

• If acid is hydrochloric acid, salt ends with -ide (chloride).

Acid-Base (Neutralisation) Reaction

• Word: Acid + Base → Salt + Water

• Example: Hydrochloric acid + Sodium hydroxide → Sodium chloride + Water

• Formula: HCl + NaOH → NaCl + H₂O

Acid-Carbonate Reaction

• Word: Acid + Carbonate → Salt + Water + Carbon dioxide

• Example: Hydrochloric acid + Calcium carbonate → Calcium chloride + Water + Carbon dioxide

• Formula: 2HCl + CaCO₃ → CaCl₂ + H₂O + CO₂

Precipitation Reaction

• Word: Solution A + Solution B → Precipitate + Solution C (aqueous)

• Example: Silver nitrate + Sodium chloride → Silver chloride (precipitate) + Sodium nitrate

• Formula: AgNO₃ (aq) + NaCl (aq) → AgCl (s) + NaNO₃ (aq)

• Precipitate should be named like a salt

Metal Displacement Reaction

• Word: More reactive metal + Metal salt solution → Salt of more reactive metal + Less reactive metal

• Example: Zinc + Copper sulfate → Zinc sulfate + Copper

• Formula: Zn + CuSO₄ → ZnSO₄ + Cu

What is a salt?

A chemical compound formed when an acid reacts with a base, metal, or carbonate, where the hydrogen ion (H⁺) from the acid is replaced by a metal or another positive ion.

Write and predict observations for the above reactions.

Reaction Type	Word Equation	Formula Equation	Observations
Acid-Base (Neutralisation)	Acid + Base → Salt + Water	HCl + NaOH → NaCl + H₂O	No fizzing, solution may warm, neutral pH
Acid-Carbonate	Acid + Carbonate → Salt + Water + CO₂	2HCl + CaCO₃ → CaCl₂ + H₂O + CO₂	Fizzing/bubbles (CO₂ gas), solid dissolves
Acid-Metal	Acid + Metal → Salt + Hydrogen gas	2HCl + Zn → ZnCl₂ + H₂	Fizzing/bubbles (H₂ gas), metal dissolves
Precipitation	Solution A + Solution B → Precipitate + Solution C	AgNO₃ + NaCl → AgCl (s) + NaNO₃	Solid forms (cloudy/milky), particles settle
Metal Displacement	More reactive metal + Metal salt → New salt + Metal	Zn + CuSO₄ → ZnSO₄ + Cu	Solid metal forms (colour change), metal dissolves

What is a lattice?

A regular, repeating 3D arrangement of atoms, ions, or molecules in a solid.

What is an alloy?

An alloy is a mixture of two or more metals, or a metal with another element, combined to make a material with better properties like strength or resistance to rust.

When do you use brackets in ionic bonding formulas?

Use brackets when there is more than one polyatomic ion (a group of atoms) in the compound to show how many of that group are present.

Example:
Calcium nitrate = Ca(NO₃)₂ (two nitrate groups)

What’s the difference between an atom and a molecule?

• Atom: One single particle (e.g. H)

• Molecule: Two or more atoms joined together (e.g. H₂)

Example:

• 2H = two separate atoms

• H₂ = one molecule of two atoms bonded

Why are metallic bonds malleable and ductile?

What makes ionic compounds hard but brittle?