Chapter 6: Shapes of Molecules & Electronegativity

• Imagine the 3D molecule in front of you, and a piece of paper (that’s surface is facing you) going through it vertically • Change the orientation of the molecule so the piece of paper “cuts” through as many of the atoms as possible • Draw the atoms in the plane of the paper (the ones the paper cuts through) using regular solid lines in their 3D positions • Draw atoms coming out (in front) of the plane of paper with with a plain wedge • Draw atoms going into (behind) the plane of paper with a dashed wedge • You may have to rotate the molecule so that all of the atoms can be drawn, even if this means more will be drawn with wedges (e.g. sulfur hexafluoride)

• Bonded pairs of electrons are involved in a covalent bond • Lone pairs of electrons are not in a covalent bond

• Lone pairs repel more strongly than a bonded pair

• Lone pairs repel more strongly than bonded pairs • The bonded pairs are repelled by the lone pairs which push them closer together, which reduces their bond angle; the angle between a bonded pairs of electrons • Each additional lone pair reduces the bond angle by 2.5°

• 4 electron pairs • 4 bonding pairs, no lone pairs • Tetrahedral • 109.5°

• Central carbon atom • Regular bonds attaching 2 hydrogen atoms to it, one above and one to the left (triangle shape) • Regular wedge towards the bottom right attaches the third hydrogen atom • Between the top hydrogen and the one with a regular wedge is the fourth hydrogen with a dashed wedge

• 4 electron pairs • 3 bonding pairs, 1 lone pair • Pyramidal • 107°

• 4 electron pairs • 2 bonding pairs, 2 lone pairs • Non-linear • 104.5°

• Multiple (e.g. double/ triple) bonds are treated as a single bonding region • Carbon dioxide has 2 double bonds, so this is counted as 2 bonding regions

• 2 bonding regions, 0 lone pairs • Linear • 180°

• 3 bonding pairs, 0 lone pairs • Trigonal planar • 120°

• All of its atoms are in the same plane

• 6 bonded pairs, no lone pairs • Octahedral • 90°

• The central sulfur atom would have 6 fluorine atoms attached to it at equal angles • The top and bottom would be attached with regular bonds • The other 2 on the top would have a dashed wedge • The 2 on the bottom would have a plain wedge

• A molecule of ammonia and a positive hydrogen ion bond together as the hydrogen ion shares what was nitrogen’s lone pair with the atom of nitrogen, through a dative covalent bond (which behaves as a regular bonding pair) • Both of the electrons come from the nitrogen atom • As the hydrogen ion was missing an electron, the overall charge of the ion is 1+

• 4 bonding pairs, no lone pairs • Tetrahedral • 109.5°

• The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

• The ability of a bonded atom to attract the bonding electrons in a covalent bond

• A value assigned as a measure of the relative attraction of a bonded atom for the pair of electrons in a covalent bond

• Up a group • Across (to the right of) a period • (With the exception of group 0)

• The atomic radius is smaller • The bonded pairs of electrons are attracted more strongly to the nucleus of the atom

• The nuclear charge increases • This attracts the bonding pairs of electrons more strongly

• Fluorine • Oxygen • Nitrogen

• A bond where the electrons are shared equally between the bonded atoms • A pure covalent bond