The Model of the Atom

Question 1

What two types of particles make up an atom’s nucleus? For each type, say whether the particles have a positive charge, a negative charge, or no charge.

Answer 1

Protons and neutrons. Protons have a positive charge, and neutrons have no charge.

Question 2

True or false? Almost all of the mass of the atom is outside the nucleus.

Answer 2

False

The nucleus it tiny , but it contains most of the mass of the atom

Question 3

Describe the plum pudding model of the atom

Answer 3

In the plum pudding model, atoms are spheres of positive charge with tiny negatively charged electrons stuck in them.

Question 4

Explain why the overall charge of the atom in neutral.

Answer 4

The number of protons is equal to the number of electrons. Protons and electrons have an equal but opposite relative charge.

Question 5

Niels Bohr proposed a model of the atom where electrons exist in energy levels. What does this mean about the location of the electrons within the atom?

Answer 5

Electrons are in fixed orbits at set distances from the nucleus.

Question 6

How can the results of the alpha particle scattering experiment be explained by the Bohr model of the atom?

Answer 6

Most of the alpha particles passed straight through the thin gold sheet, suggesting an atom is mostly empty space. However, a few alpha particles were deflected back the way they had come, suggesting there’s a small region in the atom that is positively charged (to repel the alpha particles) and where most of the atomic mass is concentrated. This fits with the Bohr model of the atom which has a small, dense, positively charged nucleus at its centre.