Topic 4 - Atomic structure

Question 1

What was John daltons atom theory and when was it made?

Answer 1

1803
all matter is made up of tiny particles called atoms. atoms of the same element are identicle and different atoms can combine to form new substances.

Question 2

What was JJ thomsons atom theory and when was it made?

Answer 2

1897
‘plum pudding model’- a ball of positive energy with electrons stuck in it
discovered the electron

Question 3

What was earnest rutherfords atom theory and when was it made?

Answer 3

1909
In Rutherford’s experiments,alphaparticles were fired at a thin sheet of gold foil. It was thought that the alpha particles would all pass straight through the foil and most did however some weredeflected off course.
he then concluded that there was a dense region ofpostive charge at the centre of the atom that repelled the alpha particles.
As a result he developed the nuclear model of the atom, in which there was a central positive nucleus, surround bynegativeelectrons.

Question 4

What did niels bohr discover about the atom and when?

Answer 4

1913
suggesting that the electrons orbited the nucleus in different energy levels or at specific distances from the nucleus.

Question 5

What was james chadwicks discovery of the atom and when?

Answer 5

1932 he discovered the neutron

Question 6

Electrons orbit the _______ at specific energy levels called _____. the further away a shell is from the nucleus, the __________ the energy level will be. if an electron absorbs _______________ radiation, it can jump to a _________ energy level/shell. This means that the electron has become ‘________’. They can later fall back to a lower level which would ______ electromagnetic radiation. if an electron absorbs enough energy, it can……….. this is known as __________.

Answer 6

1. nucleus
2. shells
3. higher
4. electromagnetic
5. higher
6. exited
7. emitt
8. leave the atom altogether
9. ionisation

Question 7

What is radioactive decay?

Answer 7

the random process in which an unstable nucleus looses energy by emitting ionising radiation in order to become more stable

Question 8

What is an alpha particle made up of?

Answer 8

2 protons and 2 neutrons

Question 9

What is alpha particles ionising power and why?

Answer 9

high ionising power because they are large and heavy

Question 10

What is the range of alpha particles in the air?

Answer 10

<5cm

Question 11

What is alpha particles penetrating power and what can stop it?

Answer 11

low penetrating power, can be stopped by paper or skin

Question 12

What is a beta particle?

Answer 12

high speed electron emmitted from a nucleus after a neutron decays into a proton and electron

Question 13

What is a beta particles ionising power?

Answer 13

moderate/low

Question 14

What is beta particles range in air and what can stop it?

Answer 14

1m+ can be stopped by aluminium foil

Question 15

What is meant by the term ‘ionising’?

Answer 15

turning an atom into an ion by adding or removing electrons

Question 16

What is a gamma ray?

Answer 16

waves of electromagnetic radiation often emitted after alpha or beta radiation in order for the nucleus to release excess energy

Question 17

What is gamma rays range in air and what can stop it?

Answer 17

> 1km can be stopped by a few cm’s of lead and a metre of concrete