IGCSE Chemistry 0654 C2.1 and C2.2

Describe the term element

substances made of only 1 type of atom and cannot be split into anything simpler

Describe the term compound

: substances made up by 2 or more elements chemically bonded together. Compounds cannot be separated physically but can be separated by chemical methods

Describe the term mixture

a combination of 2 or more substances (elements or compounds) physically mixed together but not chemically bonded. A mixture can be separated by a physical method (filtration, distillation, evaporation)

Describe the structure of the atom

An atom is made of:
• The central nucleus that contains protons (positively charged) and neutrons (no charge)
• Electrons in shells (negatively charged) move very fast around the nucleus

State the relative charges and relative masses of a proton

Relative mass: 1
Relative charge: 1+

State the relative charges and relative masses of a neutron

Relative mass: 1
Relative charge: 0 (neutral)

State the relative charges and relative masses of a electron

Relative mass: 1/1840
Relative charge: 1-

Define atomic number

The atomic number (proton number), Z is the number of protons in the nucleus of an atom.

Define mass number

The mass number (ucleon number), A is the total number of protons and neutrons in the nucleus of an atom

Describe why are noble gases unreactive?

Noble gases are unreactive because they have a full outer electron shell, making them very stable.

Explain the relationship between the group number and the number of outer electrons in Groups I to VII

In Groups I to VII, the group number equals the number of electrons in the outer shell.

Explain how can the period number of an element be used to determine its electron configuration?

The period number shows how many electron shells are occupied in an atom.