1.1 formulae and equations Flashcards
(16 cards)
define ion
An ion is a charged particle formed when an atom or molecule gains or loses electrons.
Ionic compounds have no overall charge.
This is because the total number of positive charges (from metal ions) balances the total number of negative charges (from non-metal ions).
Uncombined element
has an oxidation number of zero
Eg oxygen gas has an oxidation number of 0
Magnesium metal has a oxidation number of 0
The sum of oxidation numbers in a compound
The sum of oxidation numbers in a compound
In a complex ion
the sum of the oxidation umber = charge on the ion
In SO4^2- the oxidation number of sulphur and oxygen is 2-
group 1 and 2 have an oxidation number of
of 1+ Nacl the Na has an oxidation number of 1+
of 2- BaSO4 = the barium has an oxidation number of 2+
Oxidation number of oxygen is always 2- in compounds EXCEPT IN
FLUORINE
IN PEROXIDES
SUPEROXIDES
EG H2O2= oxygen is -1
The oxidation number of hydrogen is always 1+ in compounds except in
Metal hydrides
Eg LiH = HYDROGEN IS -1
When you have ions or compounds with atoms of more than one element the most electronegative element is given the oxidation number
Eg CCl4 chlorine is more electronegative than carbon so has the negative oxidation number -1 whilst carbon has +4
Relative atomic mass
The weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12.
Relative isotopic mass
Mass of an atom of an isotope relative to 1/12 of the mass of an atom of carbon.
Chemical formula for nitrate and carbonate ions
NO3-
CO3^2-
What are the chemical formula for oxides and hydroxides
O2-
OH-
Chemical formula for sulphate and ammonium ions
NH4+
SO4^2-
Overall oxidation number for HCO3-
-1
Oxidation number of sulphur in Na2SO4
Na - +1
O2 - 2-
4 x -2 = -8
2 x +1 = 2+
Oxidation number of sulphur = +6
How do write ionic equations
- Write out equation with state symbols
- Write out equation with aqueous ions
- Cancel out spectator ions
- Rewrite equation writing state symbols
