Topic 5.1 - The Nuclear Atom

Question 1

Describe the structure of a nucleus.

Answer 1

The nucleus is positively charged and is made of protons (positive) and neutrons (neutral).

Question 2

What are the relative charges of protons, electrons and neutrons?

Answer 2

• Protons: +1
• Electrons: -1
• Neutrons: 0

Question 3

What are the relative masses of protons, electrons and neutrons?

Answer 3

• Protons: 1
• Electrons: 0 (0.0005
• Neutrons: 1

Question 4

What are the conclusions of Rutherford’s experiment?

Answer 4

• Most of an atom is empty space
• The nucleus has a positive charge
• Most of the mass is concentrated in the nucleus

Question 5

Describe Rutherford’s atomic model

Answer 5

There is a positive nucleus at the centre of an atom, with negative electrons existing in a ‘cloud’/region around the nucleus

Question 6

What is an isotope?

Answer 6

Atoms that are the same element with the same number of protons. However they have a different number of neutrons so therefore different masses.

Question 7

What do all atoms of the same element share?

Answer 7

The same number of protons (atomic number).

Question 8

What is nuclear fission?

Answer 8

When a large and unstable nucleus splits to form two smaller nuclei, neutrons and energy.

Question 9

What is nuclear fusion?

Answer 9

When two small nuclei fuse to form a heavier nucleus and release energy.

Question 10

What does Z represent?

Answer 10

The atomic (proton) number; the number of protons in the nucleus of an atom

Question 11

What does A represent?

Answer 11

• The nucleon number; the numbers of protons and neutrons in the nucleus of an atom.
• This is also known as the atom’s mass.

Question 12

Describe Rutherford’s experiment

Answer 12

• Alpha particles (charge +2) were fired at a thin
  sheet of gold foil
• Most particles went straight through
• Some particles were deflected by small angles
  (< 90o)
• A few particles were deflected by large angles
  (> 90o)