Atomic Physics - Paper 1 Flashcards Preview

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Flashcards in Atomic Physics - Paper 1 Deck (62)
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1

State the typical size of an atom

1 x 10 -10 m

2

Describe the structure of an atom

A positively charge nucleus containing protons and neutrons surrounded by negatively charged electrons

3

State the size of a nucleus compared to an atom

The radius of the nucleus is less than 1/10000 of the radius of an atom

4

How can electrons move to a higher energy shell/level

By absorbing electromagnetic radiation

5

How can electrons move to a lower energy shell/level

By releasing electromagnetic radiation

6

What is the charge on an atom why?

Atoms are neutral as the number of positive protons is equal to the number of negative electrons

7

What is an Ion?

A charged atom that has gained or lost electrons

8

The same element must always have the same number of...?

Protons

9

Define the atomic number

Number of protons = number of electrons for an atom

10

Define nucleon number

mass mummer = Number of protons + number of neutrons

11

Define an isotope

The same element with the same number of protons but with a different number of neutrons.

12

Describe how the model of the atom has changed with new experimental evidence

Atoms were originally though to be tiny spheres that couldn't be divided.
The discovery of the electron led to the plum pudding model of the atom.
The alpha particle scattering experiment led to the nuclear model of the atom - a positive nucleus which contained the majority of the mass.
Niels Bohr suggested that electrons orbited the nucleus in shells
James Chadwich discovered the neutron

13

Describe the plum pudding model of the atom

A positive sphere with negative electrons dotted throughout it.

14

Describe the alpha particle scattering experiment.

Alpha Particles were fired at thin gold in a vacuum.

15

Describe and explain the observations from the alpha particle experiment.

The majority of alpha particles went straight though the gold. so atoms are mainly empty space.
Some alpha particles were defected by the gold foil. there must be something positive which contained the majority of the mass in an atom (the nucleus)
A tiny fraction of alpha particles bounced back where they came from. the nucleus must be a tiny part of the atom

16

How can an unstable nucleus become more stable?

By giving out radiation (alpha, beta or gamma)

17

Define activity

The rate at which a source of unstable nuclei decays

18

State the units of activity

Becquerel (Bq)

19

Define count rate

The number of decays recorded by a detector (GM tube)

20

Describe a alpha particle

Two protons and two neutrons together. A helium nucleus

21

Describe a beta partice

A fast moving electron ejected from the nucleus. This happens after a neutron has decayed into a proton

22

Describe a gamma ray

An electromagnetic wave with no charge or mass.

23

State the penetrating power of alpha, beta and gamma radiation.

Penetrating power is what can stop the radiation.
Alpha - skin, paper 5 - 10 cm of air
Beta - mm's of aluminium, 1 meter of air
Gamma - reduced by cm's of lead or m's of concrete

24

State the ionising ability of alpha, beta and gamma radiation.

Ionising ability is the ability to do damage to our living cells and tissues.
Alpha - highly ionising
Beta - moderately ionising
Gamma - very weakly ionising

25

In decay equations what is the mass number and proton number for an alpha particle?

mass number = 4
proton number = 2

26

In decay equations what is the mass number and proton number for a beta particle?

mass number = 0
proton number = -1

27

In decay equations what is the mass number and proton number for a gamma wave?

mass number = 0
proton number = 0

28

how can the rate of radioactive decay be increased?

It can be affected by physics quantities such as temperature or pressure. it is completely random.

29

Define half life

The time taken for the number of radioactive nuclei in a sample to half.

30

Define contamination

Unwanted presence of radioactive atoms on other materials such as clothes, buildings etc