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

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

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

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

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)

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

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?

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.

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

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 35.45 from? Relative atomic mass takes into consideration all the isotopes of the element and their abundance.

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 = 4.68 Si 30 = 3.08% 14.0036 12.0107 39.136 10.911 28.0972

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

Plenary Exam style questions on worksheet