1. P2 Radiation from Rocks Revision pt1 Mock 2015

2. Particle Relative Mass Relative Charge
PROTON – positive, same mass as neutron (“1”)
NEUTRON – neutral, same mass as proton (“1”)
ELECTRON – negative, mass nearly nothing
Particle
Relative Mass
Relative Charge
Proton 1
Neutron
Electron
1/1850 -1

3. number of protons is the same as the number electrons2 4
MASS NUMBER = number of protons + number of neutrons
SYMBOL
ATOMIC NUMBER = number of protons (proton number)
For a neutral atom the
number of protons is the
same as the number electrons

4. U Example 238 U is the symbol for uranium 92
p = 92 therefore there are 92 protons
m = 238 so there is 238 nucleons
(m – p) – 92 = 146 neutrons

5. Isotopes:- The three isotopes of oxygen
An isotope is an atom with the same number of protons but a different number of neutrons: O 8 16 17 18
Each isotope has 8 protons – if it didn’t then it just wouldn’t be oxygen any more.
Notice that the mass number is different. How many neutrons does each isotope have?