Presented by Leticia Bonita Prince Newcastle University 4 th Year MChem Student

Aims of Today Increase your understanding of bonding and electronegativity Increase your spatial skills and awareness using software designed by the CCDC

What are Spatial Skills? The ability to mentally manipulate 2-dimensional and 3- dimensional figures. Important in chemistry, biology, medicine, mathematics, physics and everyday life.

Bonding A chemical bond is an attractive force between two atoms. This is due to the electrons from different atoms interacting with each other. The electrons involved in bonding are called valence electrons.

Ionic Bonding Ionic bonding involves one atom accepting or donating its valence electrons to another. Magnesium oxide is an example of ionic bonding. The metal donates its valence electrons to a non- metal electron acceptor This bond is dominated by electrostatic effects i.e opposite charges attracting Small highly charged ions form stronger bonds than larger low charged ions Mg 2+ O 2-

Ionic Bonding Ionic bonding is commonly found within charged molecules forming salts Ammonium carbamate ([NH 4 + ][CH 2 NO 2 - ] is an example of an ionic compound

Covalent Bonding Covalent bonding involves atoms sharing its valence electrons. A single covalent bond is formed when one electron is donated by both atoms For example in methane one electron is donated by both the carbon and hydrogen for each bond. Bonding in methane CH 4

Covalent Bonding This type of bond is dominated by orbital overlap  Similar sized orbitals form stronger bonds than different sized orbitals. The covalent bonding in methanol is strong due to similarly sized orbitals.

Covalent or Ionic? YOU can predict if a bond will be ionic or covalent by looking at the electronegativities of the atoms forming the bond. If the difference in electronegativity is LARGE, then it is likely the bond will be ionic. If the difference is SMALL, then is likely that bond will be covalent. A polar covalent bond is an intermediate between an ionic and a covalent bond.

Electronegativity The tendency of an atom or a functional group to attract a bonding pair of electrons (or electron density towards itself). Pauling scale is used to measure electronegativity. Most electronegative element is fluorine (4.0) and least is ceasium and francium (0.7)

Trends in the Periodic Table Decreases DOWN a group Increases ACROSS a period

Bonding and Electronegativity Equal electronegativity: Pure COVALENT bond. The electron density will be shared equally between the two atoms A slightly more electronegative towards than B: POLAR Covalent bond. Most of the electron density will be drawn to A. A significantly more electronegative than B: IONIC bond. A has the electron pair and B has donated its electrons.

Breaking Bonds Polar covalent bonds will have a tendency for HETEROLYTIC FISSION Covalent bonds will have a tendency for HOMOLYTIC FISSION

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