7.2 - The discovery of the nucleus

Question 1

Write four features of every nucleus of every atom.

Answer 1

nucleus much smaller than atom,
nucleus positively charged,
mass of atom concentrated in nucleus
all positive charge of atom concentrated in nucleus

Question 2

Look at the diagram page 87 and question 2 a and 2 b

Answer 2

2a B
2b A: attracted by nucleus
C: unaffected by nucleus
D: repelled in wrong direction by nucleus

Question 3

Write the conclusion the scientists made about the atom as a result of the discovery of electrons - 2 marks

Answer 3

atoms not indivisible,

atoms contain negatively charged electrons

Question 4

Describe two differences between the nuclear model of the atom and the plum pudding model- 2 marks

Answer 4

any two from:
 nuclear: all positive charge concentrated in nucleus much
smaller than atom, plum pudding: positive charge spread out
throughout atom,
 nuclear: most mass concentrated in nucleus, plum pudding:
mass spread out throughout atom
 nuclear: most atom empty space, plum pudding: no empty space

Question 5

Explain why the alpha-scattering experiment led to the acceptance of the nuclear model of the atom and the rejection of the plum pudding model

Answer 5

nuclear model explains why some alpha particles scattered through large angles,
in plum pudding model such large-angle scattering should not be observed

Question 6

Write one difference and one similarity between a proton and a neutron.

Answer 6

similarity: proton and neutron have about same mass (or both found in
nucleus)
difference: proton is charged whereas neutron has no charge

Question 7

Explain why the mass of a helium nucleus is four times the mass of a hydrogen nucleus and its charge is only twice as much as the charge of a hydrogen nucleus

Answer 7

He nucleus contains 4 (neutrons + protons) whereas H nucleus only contains one = a single proton,
2 protons particles in He nucleus because He nucleus has twice as much charge as H nucleus,
∴other 2 particles in He nucleus are neutrons