1. Starter - Calculate the P,N + E
Element
Symbol
Mass No
Atomic No
Protons
Neutrons
Electrons
Chlorine-35 Cl 35 17
Chlorine-37 37
Copper-63 Cu 63 29
Copper-65 65
Bromine-79 Br 79
Bromine-81 81

2. Learning Objectives
1.11 understand the terms atomic number, mass number, isotopes and relative atomic mass (Ar) 1.12 calculate the relative atomic mass of an element from the relative abundances of its isotopes

3. Name that element Discuss with the person next to you
What is the element above? EXPLAIN your answers
2 minutes

4. Isotopes of Hydrogen H H H
Each isotope reacts with oxygen to form water, however unlike hydrogen and deuterium, tritium is radioactive. 1 1 1 H H H 1 2 3
1 proton,
1 electron,
0 neutrons
1 proton,
1 electron,
1 neutron
1 proton,
1 electron,
2 neutrons

5. Atoms of the same element with a different number of neutrons
Defining Isotopes
Atoms of the same element with a different number of neutrons
Individually write a definition for isotope (1 minute)
In pairs share your definitions and come up with an agreed definition for isotope (1 minute)

6. How are these eggs like isotopes?
Mini Plenary
How are these eggs like isotopes?

7. Other Isotopes Carbon 12 and Carbon 14 Hydrogen, Deuterium and Tritium
Chlorine 35 and Chlorine 37
Nitrogen 13, Nitrogen 14 and Nitrogen 15
Key Question
If their number of protons and electrons are the same, are their chemical and physical properties the same?

8. Properties
Sometimes extra neutrons can make the nucleus unstable, so its radioactive.
Different isotopes of the same element can have different physical properties, e.g. Density.
Different isotopes of the same element ALWAYS the same chemical properties because their reactions depend on their electron structure.

9. Do all of these isotopes react with oxygen? Explain your answer
Mini Plenary
Do all of these isotopes react with oxygen? Explain your answer

10. What is up with Chlorine?
Chlorine has 2 isotopes
Chlorine 35 and Chlorine 37
75% of one mole of atoms are Cl-35
25% of one mole of atoms are Cl-37
General Formula
Ar = (Ar of isotope 1 x Abundance of isotope 1) + (Ar of isotope 2 x Abundance of isotope 2)
100
Chlorine
Ar = (35 x 75) + (37 x 25) = 35.5
Where do we get from?
Relative atomic mass takes into consideration all the isotopes of the element and their abundance.

11. Have a go yourself Nitrogen N 14 = 99.64% N15 = 0.36%
Carbon C 12 = 98.93% C13 = 1.07%
Potassium K39 = 93.2% K41 = 6.8%
Boron B10 = 19.9% B11 = 81.1%
Silicon Si28 = 92.2% Si29 = Si 30 = 3.08%
39.136
10.911

12. Summary Fill in blanks on mini white boards
The number of protons in an atom is called it number. The relative mass of a neutron compared with a proton is Compared with the protons and neutrons have almost no mass. The total number and neutrons in an atom is called its number. Atoms of an element which have different numbers of neutrons are called .
atomic
one
Electrons
protons
mass
isotopes
Electrons isotopes protons mass atomic one

13. Plenary
Exam style questions on worksheet