P5.1 The nucleus

Question 1

Describe the composition of the nucleus ?

Answer 1

A nucleus composed of:
- Positively charged protons
- Neutrally charged neutrons

Question 2

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

Answer 2

Proton: +1
Neutron: 0
Electron: -1

Question 3

What is the overall charge of the nucleus and explain why ?

Answer 3

• Nucleus has an overall positive charge
• Nucleus contains protons (positive charge) and neutrons (neutral charge)
  => has an overall charge of positive

Question 4

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

Answer 4

Proton: 1
Neutron: 1
Electron: 1/2000

Question 5

Define proton number (atomic number) and what is it symbol ?

Answer 5

The number of protons in an atomic nucleus (Z)

Question 6

Define nucleon number (mass number) and what is it symbol ?

Answer 6

The number of protons and neutrons (nucleon) in an atomic nucleus (A)

Question 7

What is the formula for calculating the number of neutrons in the nucleus ?

Answer 7

Number of neutrons = nucleon number - proton number

Question 8

What is nuclide notation and interpret the symbols

Answer 8

• Atomic symbols are written in a specific notation called ZXA or nuclide notation
  + Letter “A” represents the nucleon number (top)
  + Letter “Z” represents the proton number (lower)
  + Letter “X” is replaced by the chemical symbol of the element

Question 9

Can element have more than 1 isotope ?

Answer 9

Yes and some isotopes are radioactive

Question 10

What are isotopes ?

Answer 10

Atom of an element that contains the same number of protons but different number of neutrons compared to another atom of the same element

Question 11

Define nuclear fission

Answer 11

A process where energy is released by the splitting of a large, unstable nucleus into 2 smaller nuclei

Question 12

Define nuclear fusion

Answer 12

A process where energy is released when 2 small, light nuclei join to form a heavier nucleus

Question 13

Describe the process of nuclear fusion

Answer 13

• Requires extremely high temperature & pressure => very hard to reproduce on Earth
• Stars use nuclear fusion to produce energy
• In most stars, hydrogen nuclei (light) are fused together to form a helium nucleus (heavier) & massive amounts of energy is produced

Question 14

Describe the process of nuclear fission

Answer 14

• A neutron collides with an unstable nucleus
  => the neutron and the nucleus are the reactants
• The nucleus splits into 2 smaller nuclei and 2 or 3 neutrons
  => the daughter nuclei & neutrons are products of the reaction
• Gamma rays are also emitted