4.1.1/4.1.2 Basic concepts of organic chemistry and alkanes GapFill

Organic molecules all contain the element carbon. It forms  onefivesixfour covalent bond(s) in stable compounds. Organic molecules can be classified based on the atom or group of atoms that defines their chemical and physical properties − the   fundamentalpracticalprimaryfunctional group. Molecules in which this group is the same, and that differ only in the length of their carbon chain, form a   homologoushomolytichomogeneoushomographic series. Consecutive members of these series differ only by a  CHCH3C2H5CH2 group. The formula for a member of the series is called the   skeletalgeneralmolecularempirical formula.

Organic molecules can be represented by various other types of formula too. These include: a representation of how atoms and groups are connected using mainly numbers and letters (and possibly some bonds), the   structuralskeletaldisplayedempirical formula; a diagram showing all of the atoms and bonds in a molecule, the   skeletalgeneraldisplayedstructural formula; a simpler diagram that omits most of the hydrogen atoms, the   empiricalgeneralskeletalstructural formula; and empirical and molecular formulae. Molecules with the same molecular formula but a different structural formula are called structural  isomorphsisomersisotopesisotypes.

Alkanes are  carbohydrateshydrateshydrocarbonscarbohydrons, meaning that they contain only carbon and hydrogen atoms. The electronegativities of carbon and hydrogen atoms are very similar to one another, meaning that C−H bonds do not have a strong dipole. As a result, alkane molecules are held together only by   permanent dipole−dipole interactionshydrogen bondingionic bondingLondon dispersion forces. Alkanes contain only single bonds, i.e. they are   achiralchiralsaturatedunsaturated. The general formula for a non-cyclic alkane with n carbon atoms is   CnH2n+1CnH2nCnH2n+2CnHn+1. A group with the same general formula, except for one less hydrogen atom, is called an  alkynealkinealkenealkyl group. The geometry around each of the carbon atoms in an alkane is   tetrahedraloctahedralpyramidallinear.