1. Atomic Structure and Isotopes

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. How many protons, neutrons and electrons?
Mass and atomic number
How many protons, neutrons and electrons? 1 11 16 H B O 1 5 8 23 35
238 Na Cl U 11 17 92

7. 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?

8. Which one is not an isotope of hydrogen?

9. Isotopes of Carbon C 6 12 13 14
Each isotope has 6 protons – if it didn’t then it just wouldn’t be carbon any more.
Notice that the mass number is different. How many neutrons does each isotope have?