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Lecture

CHEM 2OA3 Lecture Notes - Covalent Bond, Electronegativity, Ion


Department
Chemistry
Course Code
CHEM 2OA3
Professor
Jeff Landry

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Introduction
See Syllabus and Help Sessions pdf files
Chapter 1
Ionic Bond One atom donates electron to other (positive = cation, negative = anion)
Covalent Bond Two atoms share electron pair
Atoms most stable when have octet and filled outer shell (can tell if they want to form
ionic or covalent bonds)
Group 1 always +1, Group 2 always +2, both groups always salts (except Lithium
sometimes)
Group 17 usually -1, Group 16 usually -2
Elements in middle have problems with Electron Affinity and Ionization Potential, so
they like to share electrons (Covalent)
Most bonds are between Covalent and Ionic
More electronegative atom in a covalent bond keeps the electrons closer to itself, so the
covalent bond becomes unevenly charged and thus polar, so Polar Covalent (e.g. H-F, F
is more electronegative so electrons are closer to it)
Electronegativity Trend: →↑
Diatomics (XY), Triatomics (XY2), Tetratomics (XY3), etc.
Tetrahedral Angle: 109.5°
Electron pairs push a little stronger, so angle will usually be less than ideal (use logic)
(e.g. H2O has 2 electron pairs, so it is bent, but the angle between the 2 hydrogens is
slightly less than 109.5°
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