IGCSE Chemistry

Homologous series-  A series of organic compounds with a similar general formula, possessing similar chemical properties due to the presence of the same functional group, and shows a gradation in physical properties as a result of increase in molecular size and mass. Functional group - A group of atoms responsible for the characteristic reactions of a particular compound. Isomerism -  T wo or more compounds with the same formula but a different arrangement of atoms in the molecule and different properties.

Molecular formula -  It tells us the ratio of atoms present in the molecule. It tells us nothing about the structure. e.g.C 4 H 10 Empirical formula - It represents the simplest whole number ratio of atoms of elements in a compound. Structural formula - It shows how the atoms are arranged in the molecule.  Displayed formula - It shows all the atoms and all the bonds in the molecule.  the symbols for each atom are joined by straight lines. Each line represents a covalent bond General formula - A chemical formula applicable to a series of compounds Example: The general formula of pentane is C n H 2n+2 The molecular formula of pentane is C 5 H 12 The structural formula will be C H 3 C H 2 C H 2 C H 2 C H 3 The condensed structural formula will be C H 2 ( C H 2 ) 3 C H 3

Hydrocarbon - A hydrocarbon is a compound/molecule that only contains carbon and hydrogen atoms. If substances such as bromine join the hydrocarbon it no longer classifies as a hydrocarbon.