atomic structure

Question 1

What is the nucleus of an atom composed of?

Answer 1

Protons and neutrons (except Hydrogen which has no neutrons).

Question 2

What is the electrical charge attached to:
a neutron
an electron
a proton

Answer 2

neutron - neutral
electron - negative
proton - positive

Question 3

Which scientific discovery resulted in the solid atom theory being adapted into the “plum pudding” model of the atom?

Answer 3

Discovery of the electron (in 1897).

Question 4

Rutherford carried out an experiment to show alpha particles either passing through gold leaf, being scattered off it. Summarise the conclusions he made from this experiment.

Answer 4

Most passing through suggests atoms are mostly empty space. Some being deflected suggests the nucleus has the same charge as the alpha particle (positive). A few reflected suggests the nucleus is where most of the mass of the atom is.

Question 5

What contribution did Niels Bohr make to the arrangement of electrons in the atomic model?

Answer 5

He realised that electrons orbit the nucleus in clearly defined energy levels, at different distances from the nucleus.

Question 6

Which part of am atom is involved with radioactive decay?

Answer 6

the nucleus only

Question 7

Explain the meaning of the term activity as applied to radioactive materials and state the units of activity.

Answer 7

The rate at which a source of unstable nuclei decays.

Question 8

What is meant by the term “count rate”?

Answer 8

The number of radioactive decays recorded in a given time.

Question 9

Alpha (α) - composition = electric charge

Answer 9

2 protons and 2 neutrons = +2

Question 10

Beta (β) - composition = electric charge

Answer 10

an electron = -1

Question 11

Gamma (γ) - composition = electric charge

Answer 11

Electromagnetic wave = 0

Question 12

Explain what is meant by the term “half life”

Answer 12

The time it takes a radioactive sample to lose half its radioactivity (as measured by count rate).