P-4 Atomic Structure

Question 1

• How big are atoms

Answer 1

• 1 x 10(-10) meters radius

Question 2

• What is the basic sctuture of an atom

Answer 2

• Positively charged nucleus of protons and neutrons surrounded by negatively charged electrons

Question 3

What is the radius of a nucleus

Answer 3

• Less than 1/10000 of radio of Atom

Question 4

Where is most of the mass of an atom

Answer 4

-In the nucleus

Question 5

How are electrons arranged

Answer 5

• Arranged at different distances from nucleus in shells

Question 6

How does electrons arrangement change with absorption of electromagnetic radiation

Answer 6

• higher energy levels cause them tome further away from the nucleus

Question 7

How doe Electron arrangement change with emission of electromagnetic radiation

Answer 7

• Lower energy levels causes them to go closer to the nucleus

Question 8

What is the relationship between protons and electrons in an atom

Answer 8

• They are the same

Question 9

What is a proton number

Answer 9

• All atoms in an element have the same number of protons

- This number of protons is called the proton number

Question 10

What is the mass number

Answer 10

• Number of protons and neutrons added together

Question 11

• What are isotopes

Answer 11

• Atoms of the same element with a different number of neutrons
• Usually only one or two stable ones

Question 12

• What happens ion atoms loose one or more outer shell electrons

Answer 12

• They turn positive

Question 13

• How may a scientific model be changed

Answer 13

• Experimental evidence

Question 14

What were atoms thought to be before electrons were discovered

Answer 14

• Tiny spheres that couldn’t be divided

Question 15

• What did the discovery of the electron lead to

Answer 15

• The plumb using model

Question 16

• What did Rutherford’s scattering experiment conclude

Answer 16

• The plumb pudding model could not be true
• Beam of alpha particles aimed at gold foil
• Deflected - only positive
• Couldn’t be true

Question 17

What did Bohr say

Answer 17

• Electrons orbit at certain distances called energy levels- this agreed with experimental evidence at the time

Question 18

What lead to the discovery of protons

Answer 18

• Later experiments led to idea that positive charge of any nucleus could be subdivided into smaller equally charged particles called protons

Question 19

What lead to the discovery of the neutron

Answer 19

• The experimental work of James Chaswick provided evidence for Neutron- 20 years after nucleus

Question 20

What is radioactive decay

Answer 20

• Some atom nuclei are unstable
• The nucleus gives out radition as it changes to become more stable
• This is called radioactive decay

Question 21

• What is activity

Answer 21

• The rate at which radioactive material decays- measured in Bq

Question 22

What is count rate

Answer 22

• Number of decays each second detected by a detector

Question 23

What are the qualities of Alpha particles

Answer 23

• Two neutrons, two protons
• Travel a few cm though air
• Absorbed by paper
• Strongly ionising

Question 24

• What are the qualities of Beta particles

Answer 24

• High speed electrons from nucleus
• Travel a few meters through air
• Absorbed by aluminium
• Moderately ionising

Question 25

• What are the qualities of Gamma

Answer 25

• Electromagnetic radiation from nucleus
• Kms range in air
• Absorbed by thick wall of concrete
• Weakly ionising

Question 26

What are nuclear equations

Answer 26

• Used to represent radioactive decay

Question 27

How may alpha and Beta be shown

Answer 27

• Alpha-
  4
  2 He

Beta-
0
-1 e

Question 28

What amy the emission of radiation cause

Answer 28

• A change in mass or charge

Question 29

• What does alpha decay cause and what i s an example

Answer 29

• Alpha decay causes both a change in mass and charge to decrease

219 214 4
86 Randon —– 84 Polonium + 2 He

Question 30

What does beta decay cause

Answer 30

• Beta does not cause a change to mass but does cause charge to increase

14 14 0
6 Carbon + 7 Nitrogen + -1 e

Question 31

What does gamma decay cause

Answer 31

• No change

Question 32

What is half rate

Answer 32

• Half rate is amount of time it takes for half number of nuclei to be present tor half the count rate

Question 33

What is the nature of radioactive decay

Answer 33

• It is random

Question 34

What is radioactive contamination

Answer 34

unwanted presence of materials containing radioactive atoms on other material;s

Question 35

What is the hazard of radioactive decay determined on

Answer 35

• Type of radiation and rate

Question 36

What is irradiation

Answer 36

• Proces of exposing an object to radiation
• Does not become radioactive itself
• Often kept behind bars

Question 37

What is the risk of each type of radiation on the outside of the body

Answer 37

• Gamma and Beta high

_Alpha - high

Question 38

What is the risk of each type of radiation on the inside of the body

Answer 38

• Alpha highest- Act on specific area
• Beta- low
• Gamma - none