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VSEPR. Valence Shell Electron Pair Repulsion Theory www.longview.k12.wa.us/ralong/tietjen/Chemistry/VSEPR.JAT.ppt. TEKS.
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VSEPR Valence Shell Electron Pair Repulsion Theory www.longview.k12.wa.us/ralong/tietjen/Chemistry/VSEPR.JAT.ppt
TEKS • 7 (E) predict molecular structure for molecules with linear, trigonal planar, or tetrahedral electron pair geometries using Valence Shell Electron Pair Repulsion (VSEPR) theory.
Vocabulary: “lone pair” = “non-bonding pair” = “unshared pair” = any electron pair that is not involved in bonding “domain” = any electron pair, or any double or triple bond is considered one domain. “bonding pair” = “shared pair” = any electron pair that is involved in bonding
2 domains on central atom LINEAR • 2 domains • both are bonding pairs • They push each other to opposite sides of center (180 apart). BeCl2
3 domains on central atom TRIGONAL PLANAR • 3 domains • all are bonding pairs • They push each other apart equally at 120 degrees. GaF3
4 domains on central atom TETRAHEDRAL • 4 domains • Each repels the other equally - 109.5 - not the expected 90. • Think in 3D. CH4
Steps for using VSEPR: • Draw a Lewis Dot Structure. • Predict the geometry around the central atom. • Predict the molecular shape. … also, we can try and predict the angles between atoms.
All e- pairs push each other as far apart as possible. • Shared (bonding) pairs are “stretched” between two atoms that want them. • “Longer & Thinner” • Unshared (non-bonding) pairs are not “stretched.” • “Shorter & Thicker”
Electron Pair Repulsion • 2 lone pairs require the most space & repel each other the most, resulting in the greatest distance (angle). • 1 lone pair (thick) & 1 bonding pair (thin) require less space • 2 bonding pairs (both thin) require the least space & repel each other the smallest distance (angle).