1.1 - Atoms, Molecules, & Elements

Question 1

What is an element? 1

Answer 1

a substance which contains only one type of atom

Question 2

Many substances are compounds.

What is a compound? 2

Answer 2

more than one element

allow 'more than one type of atom'

combined in fixed proportions

allow 'joined together' or 'bonded'

Question 3

Explain why an unbalanced chemical equation cannot correctly represent a reaction. 2

Answer 3

he number of atoms must be the same before and after the reaction

otherwise matter is shown to be lost or gained

(an unbalanced) equation won’t show the correct ratio of atoms reacting

Question 4

Give the meaning of the term ‘isotopes’.

Answer in terms of subatomic particles. 2

Answer 4

isotopes are atoms with the same number of protons

allow 'atoms with the same atomic number' 

but with different numbers of neutrons

Question 5

What is the formula of an oxygen ion?

Answer 5

O2-

Question 6

Describe the structure of an argon atom. 3

Answer 6

18 protons

22 neutrons

18 electrons

electron arrangement 2, 8, 8

Question 7

Atoms were first thought to be tiny spheres that could not be divided.

J. J. Thomson discovered a particle that led to the plum pudding model of the atom.

Which particle did J. J. Thomson discover?

Answer 7

ELECTRON

Question 8

Ernest Rutherford fired particles at gold atoms.

Some of these particles were scattered.

The results led to the nuclear model of the atom.

Which type of particle was fired at the gold atoms?

Answer 8

alpha particles

Question 9

The plum pudding model did not have a nucleus.

Describe three other differences between the nuclear model of the atom and the plum pudding model. 4

Answer 9

plum pudding model
- positive charge is spread out evenly across the whole atom.
nuclear model
- the positive charge is concentrated at the centre of the atom. (nucleus)
- most of the atom is empty space, with the dense nucleus at the center and electrons orbiting around it.

Question 10

Which scientist first suggested that electrons orbit the nucleus at specific distances?

Answer 10

Niels Bohr

Question 11

The plum pudding model was an earlier model of the atom.

It suggested that the atom was a ball of positive charge with electrons embedded in it.

a)

Evidence from the alpha particle scattering experiment led to a change in the model of the atom from the plum pudding model to the nuclear model.

Explain how. 4

Answer 11

Most alpha particles passed straight through, which suggested that most of the atom is empty space.

Few particles were deflected at small angles which suggests that there must be a small, dense centre

Very few alpha particles were deflected at large angles, which suggests that there must be a positively charged centre