General Chemistry

What effect does bigger conjugation have on the HOMO/LUMO gap and energy absorption?

bigger conjugation = smaller homo/lumo gap; less energy absorbed

What does Valence Bond (VB) theory believe in, and what does it use to match reality?

electrons are localised between the atoms; hybridisation is used to match bond angles and lengths

Why are sigma bonds alone stronger than pi bonds?

electron density concentrates directly between the positive nuclei, maximising electrostatic attraction. pi bonds above and below the bond axis so less tightly held

How are bonding and anti-bonding orbitals formed according to Molecular Orbital theory?

anti-bonding: destructive interference (bottom - top); bonding: constructive (top-top)

How do you know if a resonance structure is major or minor?

1. full octets 2. neutral charge better 3. negative charge on electronegative atom, vv 4. 3 > 2 > 1 carbon increasing stability

What are the 4 quantum numbers when naming orbitals and what physical property does each define?

n: Energy level of the orbital (n = 1, 2, 3…); l: Shape of the orbital (l = 0 for s, 1 for p, 2 for d, 3 for f); m_l: Orientation in 3D space (ranges from -l to +l); m_s (Spin): Electron magnetic spin orientation (+1/2 up or -1/2 down)

What is Heisenberg's uncertainty principle?

Impossible to determine an electron's position and velocity at the same time.

What is penetration?

ability to get close to the nucleus.

How do nodes affect bond length and why?

nuclei are exposed and repel each other thus increases bond length