Relative Atomic Mass Mass of atoms is incredibly

Relative Atomic Mass �Mass of atoms is incredibly small! So we have to use relative atomic mass. �The symbol for relative atomic mass is Ar �Carbon- 12 atom contains 6 protons, 6 neutrons and 6 elections. Its relative atomic mass is defined as exactly 12. �Every other atom is compared to this. �E. g Helium is one 3 rd of a carbon atom. So its relative atomic mass is 4.

Calculate the relative atomic masses of an element using masses and abundance (A/A*) The relative atomic mass of bromine is 80 This is because in any sample of bromine, there are just about equal numbers of its two isotopes 79 Br and 81 Br. So the ‘average’ bromine atom has a relative mass of 80.

What about Chlorine and Copper? �Chlorine has two isotopes �Copper has two main isotopes Chlorine 35 75% 37 25% Copper 63 69% 65 31%

Finding the RAM of Chlorine 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 37 37 37 37 37 37 37 �If you assume you have 100 atoms then the average is easier to find.

Finding the RAM of Chlorine 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 37 37 37 37 37 37 37 �You have 75 atoms of chlorine-35 25 and atoms of chlorine-37

Finding the RAM of Chlorine 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 37 37 37 37 37 37 37 �That’s a mass of 75 x 35 �and 25 x 37 To give the mass of the 100 atoms

Using Weighted Averages 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 37 37 37 37 37 37 37 �So the average mass of a chlorine atom isn’t (35+37)/2 �Its � (35 x 75) + (37 x 25) � 100

From Weighted Averages to RAM �Weighted = (mass x number) + (mass x number) ave total number �So RAM = (35 x 75) + (37 x 25) 100 � RAM = (2625 + 925)/100 � RAM = 35. 5 amu

Weighted Averages �Use �RAM = (mass no x %) + (mass no x %) 100 �To work out the RAM of Copper

RAM of copper � RAM = (mass no x %) + (mass no x %) 100 �So RAM = (63 x 69) + (65 x 31) 100 � RAM = (4347 + 2015)/100 � RAM = 63. 6 amu

Here are various Isotopes- Attempt to calculate the number of electrons neutrons and protons for each. C – 12 C- 14 He – 4 He- 5 Li – 7 Li- 6

Isotopes �Isotopes are atoms of the same element with different numbers of neutrons. Define an isotope in your own �That is; words before � Same Atomic your Numbersee my � Same no. of protons definition � Different Mass Number � Different no. of neutrons

Watch the clip and answer the questions! http: //www. youtube. com/watch? v=Ebo. We. Wmh 5 Pg

Isotopes of hydrogen Isotope Protium Deuterium Tritium Symbol P 1 1 1 N 0 1 2 E 1 Used as fuel, for hardening margarine. 1 Used in heavy or deuterated water, solvent 1 Radioactive, Used in H-bombs, glow in the dark paints

Isotopes of hydrogen Protium Deuterium Tritium 1 proton, 0 1 proton, 1 neutron, 1 proton, 2 neutron, 1 electron

Objective check - Isotopes Element Symbo l Mass No Atomic No Chlorine-35 Cl 35 17 Chlorine-37 Cl 37 17 Copper-63 Cu 63 29 Copper-65 Cu 65 29 Bromine-79 Br 79 35 Bromine-81 Br 81 35 Protons Neutrons Electrons
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