Chemistry EOY Y9

Dalton’s Model

Thought of the model as a solid sphere and his model did not include neutrons, electrons or protons

Plum Pudding Model

By JJ Thomson, this led to the discovery of electrons and then the discovery of the nucleus

Alpha Particles Experiment

Experiment by Ernest Rutherford, firing small positively charged particles (alpha particles) at a thin piece of gold foil. Expected particles to travel straight through but some bounced back because of the nucleus in the middle of the particles

Nuclear Model

Replaced plum pudding model with nuclear model and suggested that the electrons surrounded the nucleus but not at set distances

Niels Bohr Model

Calculated that electrons must orbit the nucleus at fixed distances, called shells or energy levels

Size of Atom

Radius of about 1×10^-6 m and nuclei have a radius of 1×10^-4 m

Relative Mass

Protons and neutrons have the same mass - 1 and it takes about 2000 electrons to equal the mass of 1 proton, hence the relative mass is 0 or very small

Discovery of the Neutron

James Chadwick discovered this particle and concluded that the neutrons and protons are in the nucleus and the electrons orbit the nucleus in shells.

Elements

Elements are substances made of one type of atom

Compounds

Compounds are made of different types of atoms chemically bonded together

Filtration - Separating Mixtures

Separates insoluble solids and a liquid

Evaporation - Separating Mixtures

Separating a soluble solid from a solution

Simple Distillation - Separating Mixtures

Separating a solvent from a solution

Fractional Distillation - Separating Mixtures

Separating two liquids with similar boiling points

Chromatography - Separating Mixtures

Helps identify substances from a mixture in solution

Proton

Charge: +1 and Relative Mass: 1

Neutron

Charge: 0 and Relative Mass:1

Electron

Charge: -1 and Relative Mass: 0

Isotopes

Atoms of the same element with different number of neutrons, giving them a different overall mass. Relative atomic mass is the average mass of all the atoms of an element based on the abundance of each isotope.

First list of Elements - Development of Periodic table

They were ordered by atomic mass, they had no gaps, they were not grouped and there was no clear distinction between metals and non-metals.

Mende

Modern Perio

Group 0

Called the noble gases, unreactive and have a full outer shell so do not gain or lose electrons. Boiling point also decreases down the group

Group 1

Called alkali metals, reactivity increases down group 1 because valence electron gets further and further away from nucleus - weaker electrostatic attraction, hence has a higher tendency to lose that electron, hence more reactive. Melting and boiling point decreases down group 1 (because metallic bonds weaken)

Group 7

Called the halogens, non-metals that exist as molecules made up of pairs of atoms. melting and boiling point increases down the group and reactivity decreases down the group. This is because it becomes harder to gain one electron because shell size increases down the group which weakens the electrostatic bond between the nucleus and valence electrons.

Particle Model Limitations

Assumes that there are no forces between particles, that all particles are spherical and that the spherical particles are solids. The stronger the bond between the particles, the higher the melting or boiling point of the substances

Ions

Atoms lose or gain electrons to form ions

Ionic Bonding

When metal atoms react with non-metal atoms, transferring electrons to the non-metal atom

Giant Ionic Lattice

When metal atoms transfer electrons to non-metal atoms, you end up with positive and negative ions. The electrostatic force of attraction that holds these together is called ionic bonding. It works in all directions and many billions of ions come together to form a giant ionic lattice

Covalent Bonds

When electrons are shared between multiple atoms. The number of electrons depend on how many more electrons an atom needs to make a full outer shell.

Ionic Bonds Properties

Do not conduct electricity because they do not have delocalised electrons to carry charge through the whole structure. When molten or dissolved in water they can conduct because the ions are free to move. They have high melting and boiling points as it takes a lot of energy to break the strong ionic bonds (forces of electrostatic attraction)

Giant Covalent Structures

Many billions of atoms, each one with strong covalent bond to a number of others. E.g. graphite, diamond, silicon dioxide,

Simple Molecules

Contains only a few atoms with strong covalent bonds. Different molecules are held together by weak intermolecular forces. E.g water

Large Molecules

Many repeating units joined by covalent bonds to form a chain. E.g polymers

Metals Structure

The atoms that make up metals form layers. In metals, there are positive ions in a sea of delocalised electrons. They form giant metallic structures

Metals Properties

Malleable because layers can slide over each other, conductors because they have delocalised electrons which can carry charge through the whole structure, and high melting and boiling points because the electrostatic force of attraction is very strong.

Giant Covalent bonds properties

High melting and boiling points because the strong covalent bonds between the atoms must be broken, requiring a lot of energy. (graphite conducts electricity, the rest do not)

Simple Molecules properties

Low melting and boiling points due to weak intermolecular forces. (normally gas or liquid at room temperature)

Large Molecules properties

Lower boiling points than Giant Covalent structures. Have stronger intermolecular forces than simple molecules and normally are solid at room temperature.

Graphite

Has layers that can slide over one another, has delocalised electrons that can carry charge through the structure and is soft as the layers on graphite are not covalently bonded

Fullerenes

Hollow cages of carbon atoms bonded together in one molecule, can be arranged as a sphere or a tube (nanotube). Held together by weak intermolecular forces, so can slide over each other. They can conduct electricity

Nanotubes

Arranged in cylindrical patterns, have high tensile strength. They are useful in electronics

Alloys

Mixture of metal and metal/non-metal to make a harder mixture because it disrupts the regular layers of the metal, so they do not slide over one another.

Which metals can be extracted using electrolysis?

Potassium, Sodium, Lithium, Calcium, Magnesium, Aluminium

Which metals are reduced by carbon? (extraction)

Zinc, Iron, Tin, Lead, Copper

Which metals are mined from Earth’s crust and do not have to be extracted?

Silver, Gold, Platinum

What is Reduction?

Gain of electrons or loss of oxygen

What is Oxidation?

Loss of electrons or gain of oxygen

AAWS

Alkali + Acid —> Water + Salt

BAWS

Base + Acid —> Water + Salt

CAWS (COD)

Carbonate + Acid —> Water + Salt + Carbon dioxide

MASH

Metal + Acid —> Salt + Hydrogen

Examples of Alkalis

Ammonia, Metal Hydroxide

Examples of Bases

Metal Oxides, Metal Carbonates

Alkalis

Release OH- ions when dissolved in water

Acids

Release H+ ions when dissolved in water. Strong Acids ionise fully when dissolved in water but weak acids only ionise partially.

Cathode

Negative electrode. Reduction happens here

Anode

Positive electrode. Oxidation happens here