ATOMIC STRUCTURE

Question 1

What and when did John Dalton discover?

Answer 1

In 1804 he discovered the atom

Question 2

what did J.J. Thompson discover?

Answer 2

around 100 years later, he discovered electrons and that Dalton’s theory wasn’t completely correct.
He made the plum pudding model suggested that an atom is a ball of positively charged mass and negatively charged electrons stuck in it.

Question 3

what was Rutherford’s experiment? What did he expect and what happened. What did he deduce?

Answer 3

Rutherford tried shooting alpha particles at a thin gold foil.
they expected it to go through however many deflected back. From this, he deduced that there was a positively charged nucleus at the centre of the atom.

Question 4

what happened after Rutherford discovered the nucleus?

Answer 4

Neil Bohr then said that electrons orbit the nucleus in energy levels

Question 5

what is the size of an atom?

Answer 5

Atoms are very small, having a radius of about 1 × 10^-10 metres.

Question 6

what is the size of the nucleus of an atom?

Answer 6

The radius of a nucleus is less than 1/10 000 of the radius of an atom. Most of the mass of an atom is concentrated in the nucleus.

Question 7

what do unstable (nucleus) atoms tend to do?

Answer 7

they decay into other elements to make themselves more stable. In the process they release radiation, this is called radioactive decay.

Question 8

what is ionising radiation?

Answer 8

this is radiation that removes electrons in an atom to create a positive ion

Question 9

what is an Alpha particle made up of?

Answer 9

2 protons and two neutrons

Question 10

what is the relative mass and charge of an Alpha particle?

Answer 10

mass—— 4
charge— +2
( identical to a helium nucleus)

Question 11

what happens when an unstable nucleus emits an α particle?

Answer 11

its atom number goes down my two and its mass number goes down by 4

Question 12

what are gamma rays?

Answer 12

a γ-ray is electromagnet radiation

Question 13

what is the charge of gamma radiation?

Answer 13

it has no charge or mass

Question 14

how is beta radiation formed?

Answer 14

a β-particle is an electron created when a nucleus has more neutrons than protons. the neutron changes to a proton and a β- particle ( electron) and is immediately released.

Question 15

what are the penetrating powers of all radiations?

Answer 15

alpha - low
beta - moderately
gamma - high

Question 16

how ionising are all the radiations?

Answer 16

alpha - high (because of its size)
beta - moderate
gamma - low ( tend to pass through rather than collide with atoms)

Question 17

what absorbs the types of radiation

Answer 17

alpha - paper ( one sheet)
beta - aluminium ( around 5 mm)
gamma - lead ( thick sheets)

Question 18

what is background radiation?

Answer 18

background radiation is a low-level of radiation that is around us at all times

Question 19

give three examples of background radiation.

Answer 19

1) radioactivity occurring in naturally unstable isotopes such as food, air, and rocks
2) cosmic rays (radiation from space) which are emitted from the sun
3) radiation caused by us from nuclear waste or explosions

Question 20

what is Irradiation?

Answer 20

objects that are in the presence of a radioactive substance is irradiated. They do not turn radioactive, they are just exposed to it.

Question 21

how do you prevent irradiation?

Answer 21

By keeping sources of radiation in lead boxes

Question 22

what is contamination?

Answer 22

contamination is when radioactive particles are in or on an object.
this can cause you harm as they decay and can be even more dangerous if they are inside you

Question 23

how do you prevent contamination?

Answer 23

use gloves and tongs to handle radioactive substances. wear protective suits.

Question 24

which alpha, beta and gamma rays, which are the most dangerous out of the body and why?

Answer 24

beta and gamma as they have high penetrating powers and can easily get into organs. alpha cant penetrates through the skin.

Question 25

which, alpha, beta or gamma rays, are most dangerous inside the body and why?

Answer 25

Alpha as they can do a lot of damage in a very localised area

Question 26

what are three risks of radiation?

Answer 26

1) radiation can enter living cells, ionise atoms which can lead to tissue damage
2) lower doses can cause mutation ( cancer)
3) higher doses tend to kill the cell completely causing radiation sickness

Question 27

what is the activity of a radioactive source?

Answer 27

the number of unstable atoms in the source which decay per second

Question 28

what is the unit of activity?

Answer 28

becquerel (Bq), one decay per second

Question 29

how do you monitor the activity of a radioactive counter?

Answer 29

using a Geiger counter. You measure the count rate which is the number of counts per second.

Question 30

what is half life?

Answer 30

the time taken for the amount of radiation emitted to half

Question 31

what is the structure of an alpha particle? (2 points)

Answer 31

👉🏻 alpha particle consists of a helium nucleus

👉🏻 alpha particle has 2 protons and 2 neutrons

Question 32

what is the structure of a beta particle (2 points)

Answer 32

👉🏻 beta particle is an electron

👉🏻 beta particle comes from the nucleus

Question 33

what is the penetration of alpha? (4 points)

Answer 33

🍄alpha particles are very poorly penetrating
🍄alpha particles can penetrate a few cm in air
🍄alpha particles are absorbed by skin
🍄alpha particles are absorbed by thin paper

Question 34

what is the penetration of beta (4 points)

Answer 34

🍄beta particles can penetrate several metres of air
🍄beta particles can pass through thin metal plate / foil
🍄beta particles can travel further than alpha particles in air
🍄beta particles can travel further than alpha particles in materials eg
metals