physics P4

Question 1

why do atoms have no overall charge?

Answer 1

they contain equal numbers of positive protons and negative electrons (cancel each other out)

Question 2

how did these scientists change our understanding of the atom structure:
Rutherford
Chadwick
Bohr

Answer 2

Rutherford-proposed nuclear model of the atom
Chadwick-proved existence of neutrons
Bohr- electrons orbit nucleus in specific quantised shells

Question 3

what is the mass of proton, neutron and electron?

Answer 3

proton: 1
neutron: 1
electron: very small

Question 4

what is the relative charge of proton, neutron and electron?

Answer 4

proton:+1
neutron:0
electron:-1

Question 5

what is an isotope?

Answer 5

element with same number of protons but different number of neutrons

different forms of the same element

Question 6

describe the alpha scattering experiment

Answer 6

firing alpha particles at thin gold foil, where the number of alpha particles scattered at various angles were counted using a detector.

Question 7

how did the alpha scattering experiment change our model of the atom?

Answer 7

most alpha particles went straight through the foil but few were scattered in different directions

Question 8

what is the radius of the nucleus?

Answer 8

1x10^-14

Question 9

which electrons have the most energy?

Answer 9

the outer ring of electrons (valence electrons)

Question 10

what happens as valence electrons move down an energy level?

Answer 10

they give off energy, often in the form of light

Question 11

what is alpha:
made from?
ionising power?
range in air?
stopped by?

Answer 11

Two protons and two neutrons tightly bound together
Strong
A few cms
A sheet of paper

Question 12

what is beta:
made from?
ionising power?
range in air?
stopped by?

Answer 12

High energy, high speed electrons
Moderate
A few metres
A sheet of Aluminium

Question 13

what is gamma:
made from?
ionising power?
range in air?
stopped by?

Answer 13

High energy interactions
Weak
a long distance
thick sheets of lead or metres of concrete

Question 14

how is radiation used in medical tracers?

Answer 14

emit gamma rays from within the body

Question 15

what is half life?
how can you work it out from a graph?

Answer 15

time required for a quantity to reduce half of its initial value

draw a line down to the x axis and half it read and off info

Question 16

what can ionising radiation cause?

Answer 16

change chemical composition of material it interacts with

Question 17

what is the most dangerous outside the body?
what is the most dangerous inside the body?

Answer 17

gamma because it has higher penetration power

alpha because it deposits a large amount of energy in a small area

Question 18

what is irradiation?

Answer 18

the process of exposing an object to ionising radiation

Question 19

what is contamination?

Answer 19

the presence of radioactive material on or in object or person