1.5 Structures, Formulae And Equations
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What is a diatomic molecule?
Two atoms covalently bonded in a molecule. Some elements will only naturally exist as a diatomic molecule
Examples of diatomic elements
Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine
Element
A substance that consists of only one type of atom and cannot be broken down into anything simpler. They are represented by atomic symbols
Compound
A substance that consists of two or more (different) elements chemically combined. They are represented by formulae eg H2O
How do you read chemical formula?
Symbols tell us the element/type of atom. Small numbers tell us how many of each element there is
What do you do if there are brackets in a formula?
Multiply whatever’s in the brackets by the number given after them. If there isn’t a number just leave it
Valency
The combining power of an atom or ion (the number of electrons the element needs to gain/lose to have a full outer shell)
What does valency depend on?
What group the element is in in the periodic table
How do you work out the chemical formula of compounds?
SVSDF. Symbols Valency Swap Divide Formula each element
What does a compound containing a cation combined with a single non-metal end in?
-IDE
What does the compound name end in if oxygen is present?
-ATE or -ITE
What do chemical reactions use? (General name)
Reactants
What do chemical reactions produce?
Products
Acid + Metal =
Salt + Hydrogen
Acid + Base =
Salt + Water
Acid + Alkali =
Salt + Water
Acid + Carbonate =
Salt + Water + Carbon Dioxide
Acid + Hydrogencarbonate =
Salt + Water + Carbon Dioxide
Acid + Ammonia =
Ammonium Salt
What happens in atoms in chemical reactions?
No atoms are lost or made, but rearranged. As a result we can write balanced symbol equations showing the atoms involved
How do you write balanced equations?
Step 1: write the word equation Step 2: write the symbols and formulae needed Step 3: balance the equation by making sure that the total number of each type of element is the same on both sides of the arrow. NEVER change the small number, only add numbers before the symbol/formula
(s)
Solid
(l)
Liquid
(g)
Gas