OCR A GCSE Chemistry: C1 and C2.2 set

From Quizlet official GCSE resource centre

Ancient greek model of the atom

Atoms are tiny solid spheres which cannot be divided.

JJ Thompson

Discovered the electron and developed the "plum-pudding" model of the atom

plum pudding model of the atom

atoms are balls of positively charge with negative electrons embedded in it

Rutherford, Geiger, and Marsden

carried out the alpha particle scattering experiment and developed the nuclear model of the atom

Alpha particle scattering experiment

Fired alpha particles at a thin sheet of gold foil.

Conclusions of the alpha particle scattering experiment

Most of the atom is empty space except for a tiny positive nucleus.

Observations of the alpha particle scattering experiment

Most of the alpha particles went straight through the atom, a few alpha particles bounced back.

Nuclear model of the Atom

Atoms are made of a small positive nucleus orbited by negative electrons.

Niels Bohr

Adapted the nuclear model, by suggesting that electrons orbit the nucleus at specific distances.

James Chadwick

Carried out experiments which provided evidence of neutrons.

Proton

A subatomic particle that has a positive charge and that is found in the nucleus of an atom.

Neutron

A subatomic particle that has no charge and is found in the nucleus of an atom.

Electron

A subatomic particle that has a negative charge and orbits the nucleus in shells.

Relative mass of a proton

1

Relative mass of a neutron

about the same as that of a proton

Relative mass of an electron

1/1840

Relative charge of a proton

+1

Relative charge of a neutron

0

Relative charge of an electron

-1

Neutral atoms

same number of positive protons as negative electrons

Atomic (proton) number

the number of protons in the nucleus of an atom

Subatomic particles in the nucleus

protons and neutrons

Energy Levels/Electron Shells

The region surrounding the nucleus where electrons orbit the nucleus.

Proton

A subatomic particle that has a positive charge, defines the type of atom and that is found in the nucleus

Neutron

A subatomic particle that has no charge and that is found in the nucleus of an atom

Electron

A subatomic particle that has a negative charge and is found in electron shells, orbiting the nucleus

Mass number (atomic mass)

number of protons plus the number of neutrons in an atom of an element

Average atomic radius

0.1 nm (1 x 10^-10 m)

Average radius of an atomic nucleus

10,000 times smaller than an atom (1 x 10^-14 m)

Number of protons in an atom

atomic number

Number of neutrons in atom

mass number - atomic number

Number of electrons in an atom

is the same as the number of protons

Relative atomic mass

The weighted average mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12.

Solid

Definite shape and volume

Liquid

Definite volume but no definite shape

Gas

No definite shape or volume

Melting point

The temperature at which a solid becomes a liquid

Boiling point

The temperature at which a liquid changes to a gas

Particle theory

Matter is made up of tiny particles which are represented as small solid spheres which are constantly moving.

Uses of particle theory

Explaining changes of state

Movement of particles in a solid

Vibrate about a fixed position

Movement of particles in a liquid

Move around and slide past one another

Movement of particles in a gas

Move freely and quickly in all directions

Limitations of particle theory

Does not take into account forces between particles, size of particles, space between particles

Solid --> Liquid

Melting

Liquid --> Solid

Freezing

Liquid --> Gas

Boiling

Gas --> Liquid

Condensing

Matter

Anything that has mass and takes up space

(s)

Solid

(l)

Liquid

(g)

Gas

(aq)

aqueous (dissolved in water)

When a substance is heated

Particles stay the same size but move further apart, causing the substance to expand

When a substance cools

Particles stay the same size, but move closer together, causing the substance to contract

Metals

Elements which form positive ions

Non-metals

Elements form negative ions

Metals position on periodic table

on the left hand side

Non-metals position on periodic table

on the right hand side

Physical properties of metals

Shiny, malleable, ductile, good conductors of heat and electricity

Physical properties of non-metals

Dull, brittle, insulators of heat and electricty, liquids and gases at room temperature

Malleable

easy to shape or bend

Ductile

Easily stretched into a wire

Good conductor of heat

Allows heat energy to travel through with ease

Good conductor of electricity

Allows electrical current to flow through with ease

Brittle

Easily broken

Insulator of heat

A material that does not allow heat to pass through easily

Insulator of electricity

A material that does not allow electric current to pass through easily

pH of metal oxides

Acidic

pH of non-metal oxides

Basic

Ion

An atom or group of atoms that has lost or gained electrons and therefore a positive or negative charge.

Polyatomic ion

An ion that is made of more then one atom

Metal ion

an atom which has lost electrons forming a positive ion

Non-metal ion

an atom which has gained electrons forming negative ions.

Covalent bond

a shared pair of electrons

Molecule

two or more atoms held together by covalent bonds

Metallic bonding

Positively charged metal ions are surrounded by delocalised outer electrons

Particles in an ionic compound

Positive and negative ions

Particle in a simple covalent substance

Molecules

Particles in a giant covalent substance

Covalently bonded atoms

Particles in a metallic substance

Positive ions and delocalised electrons

Electrostatic forces of attraction

Strong forces of attraction between oppositely charged particles

Elements that form ionic compounds

Metals and non-metals together

Elements that form covalent bonds

non-metals

Elements that form metallic bonds

metals and alloys

Alloy

A metal mixed with other elements

Formation of metal ions

Atoms lose outer electrons

Metals

Elements that form positive ions

Formation of non-metal ions

Atoms gain electrons

Charge on non-metal ions

Negative

Group 1 ions charge

+1

Group 2 ions charge

+2

Group 6 (IUPAC group 16) ions charge

-2

Group 7 (IUPAC group 17) ions charge

-1

Electron structure of ions

Same as the nearest noble gas

Giant structure

A huge 3D network of atoms or ions

lattice

Regular arrangement of particles.

Giant ionic lattice

A huge, 3D, regular structure of oppositely charged ions, held together by electrostatic forces.

Examples of Ionic compounds

NaCl, MgO

Limitations of dot and cross diagram

Looks like the compound only contains a few ions