Structure 2

• Covalent compounds form by the sharing of electrons.
• Compounds containing non-metals have different properties than compounds that contain non-metals and metals.
• Lewis introduced a class of compounds which share electrons.
• Pauling used the idea of electronegativity to explain unequal sharing of electrons.
• A covalent bond is formed by the electrostatic attraction between a shared pair of electrons and the positively charged nuclei.
• When atoms of 2 non-metals react together, each is seeking to gain electrons in order to achieve the stable electron configuration of a noble gas.
• The tendency to form a stable arrangement of 8 electrons in the outer shell is referred to as the octet rule.
• The shared pair of electrons is concentrated in the region between the 2 positively charged nuclei.
• The electrostatic attraction between the 2 nuclei and the electrons constitutes the covalent bond.
• Single, double and triple covalent bonds involve one, two and three shared pairs of electrons, respectively.
• Bond length decreases and bond strength increases as the number of shared electrons increases.
• Triple bonds are stronger than double bonds which are stronger than single bonds.
• The strength of the bond is a measure of how much energy is required to break the bond.
• Triple bonds are shorter than double bonds which are shorter than single bonds.
• The number of shared electrons is greater in multiple bonds causing the electrostatic attraction to be stronger; therefore, causing the bonds to be shorter in length.
• A single bond contains only one sigma bond.
• A double bond contains one sigma and one pi bond.
• A triple bond contains one sigma and two pi bonds.
• Bond polarity results from the difference in electronegativities of the bonded atoms.
• Differences less than 1.8 are considered to be covalent.
• Values between 0.4 and 1.8 are considered polar covalent.
• Values greater than and equal to 1.8 are considered ionic.
• Basically, the greater the electronegativity difference, the more polar the bond.
• Bond polarity can be shown either with partial charges, dipoles or vectors.