P4 Atomic Structure

Question 1

What did JJ Thomson do?

Answer 1

Created the ‘plum pudding’ model ( a ball of positive charge with embedded negative charges within it).

Question 2

What did Ernest Rutherford do?

Answer 2

He discovered that the nucleus was small and positively charged by finding that most alpha particles went straight through a gold ‘leaf’; very few deflected back.

Question 3

What did Neils Bohr do?

Answer 3

He deduced that electrons exist in ‘shells’ or ‘energy levels’.

Question 4

What did James Chadwick do?

Answer 4

He determined that the nucleus must contain neutrons as well as protons.

Question 5

What is the relative charge and mass of a proton?

Answer 5

+1, 1.

Question 6

What is the relative mass and charge of a neutron?

Answer 6

0, 1.

Question 7

What is the relative mass and charge of an electron?

Answer 7

-1, 0 (very small).

Question 8

What is the mass number?

Answer 8

The sum of the protons and neutrons in an atom. Found at the top of the symbol

Question 9

What is the atomic number?

Answer 9

The amount of protons in an atom. Found at the bottom of the symbol.

Question 10

How do you calculate the number of neutrons in an atom?

Answer 10

Mass number - atomic number

Question 11

What is an isotope?

Answer 11

An atom of the same element which has the same number of protons but a different amount of neutrons.

Question 12

What is Gamma radiation?

Answer 12

A high energy EM wave that can be emitted by a nucleus, but this isn’t due to day; it’s due to a nucleus having excess energy.

Question 13

What is alpha decay?

Answer 13

The decay of larger nuclei. Nucleus ejects a Helium nucleus (2 protons + 2 neutrons). This is known as Alpha radiation.

Question 14

What is beta decay?

Answer 14

The decay of smaller nuclei. A neutron decays into a proton + electron. The high energy electron is Beta Radiation.

Question 15

Describe alpha radiation.

Answer 15

Mass of 4, Charge +2, ionising power is high, penetrating ability is low, smoke detectors.

Question 16

Describe Beta Radiation.

Answer 16

Fast moving electrons, mass of basically 0, charge of -1, medium ionising power, medium (absorbed by few mm of aluminium) penetrating ability, used as a thickness gauge.

Question 17

Describe Gamma radiation.

Answer 17

High energy EM wave, mass of 0, charge of 0, low ionising power, high (intensity reduced by lead and concrete) penetrating ability, used in radiotherapy/gamma knife & sterilisation.

Question 18

What is radioactivity?

Answer 18

Radioactivity is the rate of decay in a sample of radioactive material.

Question 19

What is a half-life?

Answer 19

The time it takes for the activity to halve.

Question 20

How do you calculate half lives?

Answer 20

half the activity as many times as needed to get to new activity. Figure out how many half-lives occur in the time period. E.g. 96Bq to 12Bq in 12 months. 96/2 = 48, 48 / 2= 24, 24/2=12 = 3 half-lives. 12 months = 3 half-lives so one half-life = 4 months.

Question 21

What is Fission?

Answer 21

The splitting of a (heavier) nucleus into two ‘daughter’ nuclei, releasing energy that can then be used to generate electricity. It releases up to 3 more neutrons - induce more fission known as a chain reaction.

Question 22

What is Fusion?

Answer 22

The joining together of two (lighter) nuclei, releasing energy. Large amounts of energy can be released if there is a large amount of kinetic energy to begin with.