S2.2 The covalent modelIB Chemistry SL: Flashcards

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Define a covalent bond.

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Define a covalent bond.: Electrostatic attraction between a shared pair of electrons and the positively charged nuclei.
How do bond length and strength change from single to triple bonds?: More shared pairs: shorter and stronger bonds.
Define a coordination bond.: A covalent bond in which both shared electrons come from the same atom.
Give an example of a species with a coordination bond.: NH₄⁺ (N donates its lone pair to H⁺); also H₃O⁺ and CO.
Shape and bond angle of NH₃?: Trigonal pyramidal, about 107°.
Shape and bond angle of H₂O?: Bent, about 105°.
Why is CO₂ non-polar although its bonds are polar?: It is linear, so the two equal bond dipoles cancel.
Why does diamond not conduct but graphite does?: Graphite has one delocalised electron per C that can move; in diamond all four electrons are in bonds.
Describe the structure of SiO₂.: Covalent network: each Si bonded to four O, each O to two Si.
What is graphene?: A single layer of graphite: hexagonally bonded carbon atoms, one atom thick.
Order of intermolecular force strength for comparable molar mass?: London < dipole–dipole < hydrogen bonding.
Conditions for hydrogen bonding?: H bonded to N, O or F, attracted to a lone pair on N, O or F of another molecule.
Define Rf.: Distance moved by the component ÷ distance moved by the solvent front.
A component has a high Rf. What does that tell you?: It is more strongly attracted to the mobile phase than to the stationary phase.