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Flashcards in Atomic Stucture Deck (64):
1

Radius of an atom

1 x 10(-10)

2

What charge is the nucleus

Positive

3

Nucleus surrounded by

Negative charged electrons

4

Protons have a charge of

+1

5

Electrons have a charge of

-1

6

Atoms have the same number of

Protons and electrons so no overall charge

7

Most of the mass is in the

Nucleus

8

Radius of nucleus is less than

1/10000 of the atoms radius

9

The electrons are arranged

Different distances from the nucleus in different energy levels

10

The energy of an electron may change when

The atom emits or absorbs electromagnetic radiation

11

Absorbing electromagnetic radiation

Moves electron to a higher energy level further fr m the nucleus

12

Electromagnetic radiation is emitted when

An electron drops a lower energy level

13

When an atom loses and outer electron

It become a positive ion

14

When an atom gains an outer electron

it becomes a negative ion

15

All atoms of an element have the same number of

Protons

16

No. of protons is called

atomic numbers

17

Mas number is

Total number of protons and neutrons

18

Can have a different number of neutrons called

Isotope

19

Plum pudding model(5)

Tiny sphere
Couldn’t be divided
JJ Thompson in 1897
Ball of positive charge
Electrons embedded in it

20

1905 Rutherford and mars den

Bombarded thin gold foil with alpha particles

21

Most particles passed through

But some didn’t

22

Some particles were deflected so

Must have come close to a concentration of charge

23

Conclusion of the Rutherford and mars den experiment

Mass is concentrated in a central nucleus which was positively charged
Electrons surround the nucleus

24

Niels Bohr

Electrons orbit the nucleus at specific distances

25

James Chadwick 1932

Other experiments
Neutron in the nucleus

26

Some atomic nuclei are unstable and

Give out radiation in order to become more stable

27

The type of radiation emitted depends on

Why the nucleus is unstable and is a random process

28

The activity of a radioactive source is

The rate at which it decays

29

The rate at which it decays is measured in

Becquerels

30

One becquerel is equivalent to

One decay per second

31

The count rate is

The number of decays recorded each second by a detector
Geiger-Muller tube

32

One becquerel is equivalent to

One count per second

33

Three main types of radiation

Alpha
Beta
Gamma

34

Most ionising is

Alpha

35

Least ionising is

Gamma

36

Alpha

Two neutrons
Two protons
Ejected form the nucleus
Easily absorbed
Cause damage passing though living cells

37

Beta

High speed electron
Elected from the nucleus as a neutron and turns into a proton
Likely to cause damage if absorbed by living cells
Can penetrate the body and inner organs

38

Gamma

Electromagnetic radiation
Emitted form the nucleus
Pass through the living cells without being absorbed or causing ionisation

39

The fourth type of radiation

A neutron

40

Radiation contamination is

The unwanted presence of materials containing radioactive atoms

41

The hazard front the contamination is due to

The decay of the contaminating atoms

42

The type of radiation emitted affects

The hazard

43

Irradiation

The process of exposing an object to nuclear radiation
Can be deliberate or accidental
Doesn’t make objets radioactive

44

Protecting against irradiation

Sources of low activity for short times

45

Half life is

The time It takes for half the nuclei to decay

Or

The time it takes the count rate, or activity of a sample containing the isotope to fall to 50% of its original value

46

The half doesn’t change

Different isotopes have different half lives

47

Isotopes with a short half life

Unstable
Emit radiation quickly
Hazardous
Not radioactive for long

48

Isotopes with a long half life

More stable
Radioactive for long time
Emit radiation slowly
Less hazardous

49

Medical trace ( nuclear radiation)

Radioactive isotuoe ingested
Travels around body and van be detected in the outside

50

When using an isotope for medical reasons it is important to

Use the right half life, activity and type of radiation

51

Best tracer would be

Gamma

Can penetrate the body
They are leat ionising

52

When is ther background radiation

Al the time

53

Level of background reaction depends on

Location
Occupation

54

What is nuclear fission

Splitting of a large unstable nucleus
Unstable nucleus absorbs a neutron

55

During fission

Splits into two smaller nuclei
Emits two or theee neutrons
Gamma ray and energy

56

All the products of fission have

Kinetic energg

57

Neutrons emitted start a

Chain reaction by being absorbed by other large unstable nuclei

58

Nuclear weapon is

Result of an uncontrolled chain reaction

59

During nuclear fusion

Two light nuclei join to form a heavier nucleus
Some of the mass is converted into energy
Some energy emitted as radiation

60

Nuclear equations represent

Radioactive decay

61

Alpha particle is represents by

4
He
2

62

A beta particle is represented by

0
e
-1

63

When an alpha particle I emitted

Mass number is reduced by 4
Atomic number is reduced by 2

64

Beta decay

Mass number does not change
Atomic number increased by 1