Topic 3 - Part 1: Formulae & The Mole
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What are the diatomic elements?
H I N Cl Br O F Or HINClBrOF
What does diatomic element mean?
The atoms are joined together in pairs - they are two atom molecules
When do you include the diatomic part of the elements in formulas?
Only if they are alone/just the element and nothing joining it
What do the endings -ide, -ate/ite mean?
ide means there is just those two elements Ate/ite means there’s also oxygen included and you should look for the page telling you the formula if in one of them
What do all the pre fixes mean in a formula?
Mono - 1 Di - 2 Tri - 3 Tetra - 4 Penta - 5 Hexa - 6 Hepta - 7 If in a formula don’t add any other bonds not given in the formula and don’t swap the bonds like you would others
How do you find valency number?
Group numbers up to four match with the valency number like Group 4 has a valency of 4 But from 5 onwards it decreases so 5 would be 3 and 7 would be 1 etc
Roman numerals for transition metal valency
One - (I) Two - (II) Three - (III) Four - (IV) Five - (V) Six - (VI) Seven - (VII)
How do you find the formula for something (without prefixes)
Cancel and cross Find the valency of the individual elements Then write them Then swap the valency’s and if possible cancel them down like if they are both 2 cancel it to 1 You swap because when forming a compound the valency is how many connection points there are so when joining you swap because that’s how many elements are needed to connect to all the connections So if an element has a valency of 2 and the other has a valency of 1 you need two of the 1 and only 1 of the 2
How do you know the valency of compounds like phosphate
Look in the data booklet and find the chart. charges like - and + indicate the valency of that You can’t change the compounds core things so nothing but the charge is changed and if you have multiple of that already made compound after swapping put it into brackets and leave everything within it the same
How do you figure out the Gfm?
Find the RAM of one element and multiply it by the atoms present in the formula and continue for all the other elements in the compound
What is the mole calculation with mole number, mass and gfm?
N = mass/gfm Just a triangle sum like physics
How do you find the mole ratio in a formula equation?
Look at the numbers Infront of the compound or element
How do you find a mass etc in an equation?
Circle the elements or compounds you are finding stuff for Then Write the mole ratio Using the value your given do the n = mass/gfm Calculation Depending on the mol ratio change or keep the same Then to find the mass etc of what you want input that in and rearrange the formula to get your answer