1. P Nuclear reactions
Some atoms have an unstable nucleus and need to get to a lower energy state.
It can become stable by emitting
Alpha, Beta or gamma radiation.
It “decays”.

2. The structure of the atom
ELECTRON – negative, mass nearly nothing
PROTON – positive, same mass as neutron (“1”)
NEUTRON – neutral, same mass as proton (“1”)

3. The structure of the atom-1
Electron 1
Neutron
Proton
Relative Charge
Relative Mass
Particle
MASS NUMBER = number of protons + number of neutrons He 2 4
PROTON NUMBER = number of protons (obviously)

4. Each isotope of oxygen has 8 protons
An isotope is an atom with a different number of neutrons:
Isotopes
The mass number is different. How many neutrons does each isotope have? O 8 16 O 8 17 O 8 18
Each isotope of oxygen has 8 protons

5. ISOTOPES OF CARBON C C C 12 13 14 6 6 6

6. ISOTOPES OF CARBON C C C 12 13 14 6 6 6
Q1. How many protons does each carbon atom have?
Q2. How many electrons does each carbon atom have?
Q3 How many neutrons does each carbon atom have?

7. ISOTOPES OF CARBON C C C 12 13 14 6 6 6
Q1. How many protons does each carbon atom have?
Q2. How many electrons does each carbon atom have?
Q3 How many neutrons does each carbon atom have?

8. ISOTOPES OF CARBON C C C 12 13 14 6 6 6
Q1. How many protons does each carbon atom have?
Q2. How many electrons does each carbon atom have? 6
Q3 How many neutrons does each carbon atom have?

9. ISOTOPES OF CARBON C C C 12 13 14 6 6 6
Q1. How many protons does each carbon atom have?
Q2. How many electrons does each carbon atom have? 6
Q3 How many neutrons does each carbon atom have? 6, 7, 8

10. Radioactivity electrons ?
Isotopes of the same element always have the same
number of in their nuclei, but they can have
different numbers of
electrons ?
protons ?
neutrons?

11. C Carbon isotopes: eg carbon 12 carbon 14 12 14 6 protons & 8 neutrons
proton number C
Some isotopes have unstable Without warning
the breaks up releasing , or radiation and
possibly forms a new element.
(nucleus, , , atoms)

14. + Types of radiation  decay: P D He
1) Alpha () – a nucleus decays into a new nucleus and emits an alpha particle (2 protons and 2 neutrons – the nucleus of a helium atom)
Unstable nucleus
New nucleus
Alpha particle
 decay: P D + He

15. + + Types of radiation  decay: P D He Th Ra He
1) Alpha () – a nucleus decays into a new nucleus and emits an alpha particle (2 protons and 2 neutrons – the nucleus of a helium atom)
Unstable nucleus
New nucleus
Alpha particle
 decay: P D + He
Eg 1: Th Ra + He

16. + + Types of radiation  decay: P D He 224 Th Ra He 88
1) Alpha () – a nucleus decays into a new nucleus and emits an alpha particle (2 protons and 2 neutrons – the nucleus of a helium atom)
Unstable nucleus
New nucleus
Alpha particle
 decay: P D + He
Eg 1:
224 Th Ra + He 88

17. + Types of radiation  decay: P D 
2) Beta () – a nucleus decays into a new nucleus by changing a neutron into a proton and electron. The fast moving, high energy electron is called a beta particle.
Beta particle
New nucleus
Unstable nucleus
 decay: P D + 

18. + + Types of radiation  decay: P D   K Ca
2) Beta () – a nucleus decays into a new nucleus by changing a neutron into a proton and electron. The fast moving, high energy electron is called a beta particle.
Beta particle
New nucleus
Unstable nucleus
 decay: P D + 
Eg 2: K Ca + 

19. + + Types of radiation  decay: P D   40 K Ca 20
2) Beta () – a nucleus decays into a new nucleus by changing a neutron into a proton and electron. The fast moving, high energy electron is called a beta particle.
Beta particle
New nucleus
Unstable nucleus
 decay: P D + 
Eg 2: 40 K Ca +  20

20. Types of radiation
1) Alpha () – a nucleus decays into a new nucleus and emits an alpha particle (2 protons and 2 neutrons – the nucleus of a helium atom)
3) Gamma – after  or  decay surplus energy is sometimes emitted. This is called gamma radiation and has a very high frequency with short wavelength. The nucleus is not changed.
Unstable nucleus
New nucleus
Alpha particle
Unstable nucleus
New nucleus
Gamma radiation
2) Beta () – a nucleus decays into a new nucleus by changing a neutron into a proton and electron. The fast moving, high energy electron is called a beta particle.
Beta particle
New nucleus
Unstable nucleus

21. Background radiation * This is ionising radiation from:
cosmic rays (from outer space) %
X ray tubes %
radon gas from granite rocks %
food and drink %
air %
nuclear reactors leaking %
nuclear weapons testing %
Ionisation is the removal of an electron from an atom
leaving it as a positively charged ion
Experiment to measure Background count rate /min: *

24. 27p 33n