Physics Atomic Structure July 2018

Question 1

What are found in atoms?

Answer 1

Protons, neutrons and electrons

Question 2

What are the charges of protons, neutrons and electrons?

Answer 2

Proton = +1
Neutron = 0
Electron = -1

Question 3

What are the masses of protons, neutrons and electrons?

Answer 3

Proton = 1
Neutron = 1
Electron = 0 (1/1840)

Question 4

What is a proton?

Answer 4

A positively charged particle which is found in the nucleus of an atom.

Question 5

What is a neutron?

Answer 5

A neutral particle found inside the nucleus of an atom.

Question 6

What is an electron?

Answer 6

A negatively charged particle that orbits the nucleus of an atom on energy levels or shells.

Question 7

What is an ion?

Answer 7

An ion is an atom that has gained or lost 1 or more electrons to gain a full outer shell.

Question 8

What is the atomic number?

Answer 8

Number of protons. The bottom number.

Question 9

What is the mass number?

Answer 9

Number of protons + Neutrons. The top number.

Question 10

What is an isotope?

Answer 10

An atom that has gained or lost 1 or more neutrons.

Question 11

What is an alpha particle?

Answer 11

A particle that is formed by 2 protons and 2 neutrons (a helium nucleus).

Question 12

What is a beta particle?

Answer 12

A fast moving electron.

Question 13

What is a gamma ray?

Answer 13

An electromagnetic wave.

Question 14

What is the Geiger-Müller tube?

Answer 14

A device which detects ionising radiation. An electronic counter can record the number of particles entering the tube.

Question 15

What is ionisation?

Answer 15

When alpha particles bounce off of other particles, the attractive force between the + charge of the particle and - charge of the electron pulls the electron out of the atom. This is called ionisation due to the original atom losing an electron.

Question 16

What are the ionising powers of alpha and beta particles and gamma rays?

Answer 16

Alpha- Very strong
Beta - Medium
Gamma - Weak

Question 17

What are the penetrating powers of alpha and beta particles and gamma rays?

Answer 17

Alpha- Stopped by paper
Beta - Stopped by aluminium
Gamma - Stopped by thick lead (5cm thick)

Question 18

What is background count?

Answer 18

The average count rate which a Geiger-Müller tube records over a period of time.

Question 19

What is background radiation?

Answer 19

Comes from natural man-made sources in our environment.

Question 20

What is half-life?

Answer 20

The time taken for the number of a nuclei in a radioactive isotope to halve. (in one half-live, the activity or count rate of a radioactive sample also halves).

Question 21

What is a becquerel?

Answer 21

An emmision of 1 particle/second (1/Bq)

Question 22

What is nuclear fission?

Answer 22

The process of which a large unstable radioactive nuclei are hit by a neutron. They combine to make an even more unstable nucleus that is so unstable that it splits into 2 new nuclei as well as emitting 3 neutrons.

Question 23

What is nuclear fusion?

Answer 23

The process of joining small nuclei to form large ones.

Question 24

How was the nucleus of an atom discovered?

Plum pudding model –> Nuclear model

Answer 24

An alpha stream of particles was fired into a thin sheet of gold foil. Some of the particles were reflected signifying that mass is concentrated in the centre around a structure e.g. the nucleus. (Most particles went straight through).