GCSE Chemistry- Atoms, Ions and Molecules

year 9

Properties of particles in a solid

• strong forces of attraction between particles

• particles are in a fixed and regular arrangement

• particles contain little energy

Properties of particles in a liquid

• weaker forces of attraction between particles

• Particles are close and can move past each other (irregular arrangement)

• Particles have more energy than solids

Properties of particles in a gas

• Weakest forces of attraction between particles

• Particles have more energy than in solids and liquids

• Particles move randomly/freely

Gas to Liquid

condensing

Liquid to Solid

Freezing

Solid to Liquid

Melting

Liquid to Gas

Boiling

Gas to Solid

Deposition

Solid to Gas

Sublimation

Evaporation

When particles from the surface of a liquid turn into a gas. It can happen at any temperature between the MP and BP of a liquid

Boiling

When all the particles in a liquid gain sufficient energy to turn into a gas. It can only occur at the BP of a substance.

Element

The simplest substances that cannot be broken down

Compound

Made up of two or more types of particles, joined together by chemical bonds.

Mixture

Two or more substances combined, without chemical bonds holding them together. They can usually be separated easily.

Conversion from Nanometre to Micrometre

÷ 1000

Conversion from Micrometres to Millimetres

÷ 1000

Conversion from millimetres to metres

÷ 1000

How many times bigger is a metre than a nanometre?

1 billion

What is the radius of a nucleus?

1×10^-14 m

What is the radius of an atom?

1×10^-10 m

How many times bigger is an atom than a nucleus?

10,000

Atomic Number

Number of protons (or electrons)

Mass Number

Number of Protons + Number of Neutrons

Scientific Theory

An explanation agreed upon by groups of scientists

What did John Dalton state about atoms?

• All matter is made up of atoms

• There are different types of atom

• Each element contains a different type of atom

What did JJ Thomson discover and state about atoms?

• discovered electrons

• described the atom as a ‘plum pudding’ model

  • proposed that an atom was a ball of positive charge with negative electrons embedded in it.

Who conducted the alpha particle experiment?

Rutherford and Marsden

What did Rutherford and Marsden expect from the alpha-particle experiment?

That most of the particles would go straight through

What actually happened in the alpha particle experiment?

Some atoms changed direction more than expected and some even got deflected backwards

What did the alpha particle experiment lead to?

The development of the modern atomic model

What conclusion did Rutherford and Marsden make from the alpha particle experiment?

That the mass of the atom was concentrated at the centre of the nucleus and that the nucleus was positively charged.

What did Niehls Bohr propose about the atom?

That negative electrons were held in shells at a fixed distance from the nucleus

What did James Chadwick discover and how did he come to discover this?

• discovered that the mass of atoms was twice the expected value

  • led to discovery of neutrons

Features of the plum pudding model

• No nucleus

• Positive charge and mass scattered throughout the atom

• no protons or neutrons

• no electron shells

Features of the Nuclear Model

• Electrons held in shells

• positive charge held in the nucleus

• mass held in the nucleus

Features of both the plum pudding and nuclear model

• both contain negative electrons

• contain areas of positive charge

• neutral overall charge

What two things can happen when atoms combine?

• Electrons can be transferred

• Electrons can be shared

How are elements arranged in the periodic table?

In order of atomic number (increasing number of protons/electrons)

What are columns in the periodic table called?

Groups

What are rows in the periodic table called?

Periods

What links elements in the same group of the periodic table?

Same number of electrons in their outer shell

What links elements in the same period of the periodic table?

They have the same number of shells

Isotopes

Atoms of the same element that contain the same number of protons but different numbers of neutrons

What is a charged particle called?

An ion

When is a positive ion formed?

Positive Ions are formed when a metal atom loses electrons

When are negative ions formed?

Negative ions are formed when a non-metal atom gains electrons.

Ionic Bonding

When a metal atoms donates electrons to a non-metal atom, so that they can both have a full outer shell

Another name for positive ions

Cations

Another name for negative ions

anions

In ionic bonding, how are the cations and anions attracted to each other?

Through electrostatic forces of attraction

What is the overall charge of any ionic compound?

Zero

What is the formula of an ammonium ion?

NH₄⁺

How are the atoms in an H₂ molecule held together?

The positively charged nucleus and the negatively charged electron attract each other.

Covalent Bonding

When non-metal atoms share electron pairs to obtain full outer shells

What diagrams are used to show covalent bonding?

dot and cross

What are particles in covalent bonding called?

Molecules

Properties of simple covalent molecules

• Low melting and boiling points

  • therefore liquid or gas at room temperature

Formula for Sodium Chloride

NaCl

Formula for Calcium Chloride

CaCl₂

Formula for propane

C₃H₈