Look at the diagram showing a simplified model of an atom.
a.[1]
Which subatomic particles are located within the electron shells?
b.[1]
Which two subatomic particles are found inside the nucleus?
c.[2]
Explain why almost all the mass of an atom is concentrated in the nucleus.
d.[2]
Look at these two symbols representing carbon atoms: 612Cand 614C^{12}_{\ \ 6}\text{C} \quad \text{and} \quad ^{14}_{\ \ 6}\text{C} 612Cand 614C
State the relationship between these two carbon atoms and explain your answer in terms of subatomic particles.