Topic 4- Atomic structure

Question 1

approximation of the radius of an atom

Answer 1

1x10^-10 metres

Question 2

subatomic meaning

Answer 2

smaller than or occurring within an atom

Question 3

what are three subatomic constituents WITHIN an atom?

Answer 3

• protons
• neutrons
• electrons

Question 4

describe the arrangement of protons,neutrons and electrons in an atoms

Answer 4

• the protons and neutrons are found in the atoms nucleus. (causing positively charge nucleus)
• the electrons are found in the discrete energy levels around the nucleus

Question 5

give two ways an atoms electron arrangement can be changed

Answer 5

• absorbing electromagnetic radiation

- emitting electromagnetic radiation

Question 6

Explain how an atoms electron arrangement changes when it absorbs EM radiation

Answer 6

• electrons move further away from the nucleus

- they move to a higher energy level

Question 7

Explain how an atoms electron arrangement changes when it emits EM radiation

Answer 7

• electrons move closer to the nucleus

- move to a lower energy level

Question 8

all forms of the same element have the same number of…

Answer 8

protons

Question 9

what is an isotope of an atoms?

Answer 9

an atoms of an element that has the same number of protons but different number of neutrons

Question 10

what may lead to a scientific model being changed or replaced?

Answer 10

the discovery of new experimental evidence which doesn’t agree with the existing theory

Question 11

How did the plum-pudding model describe an atom?

Answer 11

a ball of positive charge, with negatively charged electrons distributed evenly throughout it

Question 12

What was the alpha-scattering experiment and who did it?

Answer 12

Rutherford, he concluded most of the mass of the atom is concentrated at the centre in the nucleus, nucleus is positively charged

Question 13

1) John Dalton

Answer 13

1803, all matter was made up of tiny particles called atoms,
drew as tiny spheres that couldnt be divided

Question 14

2) JJ Thomson

Answer 14

suggested plum pudding model of an atom, where the atom is a ball of positive charge with negative electrons embedded in it.

Question 15

3) Rutherford

Answer 15

1909, wanted to test the plum pudding model,
test: positively charged alpha particles were fired at thin gold foil, most alpha particles went through the foil, others scattered in different direction.
suggestion for a new model (nuclear model),the mass of an atom is concentrated at its centre, the nucleus
the nucleus is positively charged

Question 16

4) BOHR

Answer 16

adapted rutherford nuclear model, edit: electrons orbit the nucleus in shells,

Question 17

why do unstable nuclei give out radiation?

Answer 17

• unstable nuclei undergo decay to become more stable

- this is called radioactive decay

Question 18

unit of radioactive decay

Answer 18

becquerel (bq)

Question 19

What is count- rate?

Answer 19

the number of radioactive decays per second for a radioactive source.
the detector used is called the geiger-muller tube

Question 20

state 4 type of nuclear radiation

Answer 20

• alpha
• gamma
• beta
• neutrons

Question 21

what are the constituent of an alpha particle?

Answer 21

-two protons and two neutrons

Question 22

range of an alpha particle through air

Answer 22

a few cm (normally 2-10cm)

Question 23

what will stop beta radiation from passing through a point?

Answer 23

• a thin sheet of aluminium

- several metres of air

Question 24

What will stop gamma radiation from passing a certain point?

Answer 24

• several centimetres of lead

- a few metres of concrete

Question 25

What type of radiation is the most and least ionising?

Answer 25

Alhpa is most and gamma is least

Question 26

describe the nature of radioactive decay

Answer 26

• random

- it is impossible to predict when a nuclei will decay

Question 27

Define the half-life of an isotope

Answer 27

the time it takes for the number of unstable nuclei to halve.

Question 28

What is irradiation?

Answer 28

• the process of exposing a material to nuclear radiation.

- the material does not become radioactive

Question 29

why did the new evidence from the scattering experiment lead to a change in the atomic model?

Answer 29

The results from the alpha scattering experiment led to the conclusion that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged. The alpha scattering experiment led to the ‘plum-pudding model’ being replaced by the nuclear model.

Question 30

what is the difference between the plum pudding model of the atom and the nuclear model of the atom?

Answer 30

• nuclear mass concentrated at the centre
• plum pudding mass evenly distributed
• plum pudding positive charge throughout model
• nuclear model positive charge only small section
• plum pudding electrons embedded in the mass of positive charge
• nuclear model has electrons orbiting the nucleus in shells

Question 31

difference between irradiation and contamination

Answer 31

irradiation- Occurs when an object is exposed to a source of radiation outside the object,Doesn’t cause the object to become radioactive.
contamination- Occurs if the radioactive source is on or in the object, A contaminated object will be radioactive for as long as the source is on or in it.

Question 32

how many millisieverts equal a sievert

Answer 32

100 millisievert= 1

Question 33

What determines how dangerous an isotope is?

Answer 33

their half-life, longer the isotopes the more dangerous,

Question 34

nuclear radiation used medically:

Answer 34

• examining internal organs

- controlling/destroying unwanted tissues

Question 35

How is radiation used for sterilisation?

Answer 35

gamma emitters are used to kill bacteria on equipments