Definition As-level chemistry unit 1 (edexcel)

CHEMISTRY DEFINITIONS UNIT 1


Topic 4:
1) Hydrocarbons: compounds that contain only carbon and hydrogen
atoms.
2) Unsaturated: If there are two bonds (a double bond) drawn between one
or more carbon atoms.
3) Saturated: If there are only single bonds
4) Molecular formula: actual number of atoms of each element in a
molecule
Example: C3H8 (propane).
5) Structural formula: shows the structure carbon by carbon with
hydrogens and functional groups attached.
Example: CH3CH2OH (ethanol)
6) Displayed formula: shows how all the atoms are arranged and every
bond between them.
7) Skeletal formula: only shows the bonds on the carbon skeleton. The
carbon and hydrogen atoms are not shown but any functional groups are.
8) Empirical formula: it is the simplest ratio of different types of atoms
present in the molecule.
Example: C4H10 has empirical formula of C2H5.
9) A function group : in a molecule is an atom or group of atoms that gives
the compound some predictable properties.
10) Homologous series : is a set of compounds with the same functional
group.

, Properties of Homologous Groups:
● Same general formula
● Same functional group
● Same chemical properties
● Trend in similar physical properties
● Each member differs by CH2 group the one before


NAME GENERAL FORMULA EXAMPLE

Alkane CnH2n+2 CH4

Alkene CnH2n C2H4

Halogenoalkane CnH2n+1X CH3CH2Br

Alcohol CnH2n+1OH CH3CH2O