Chemistry — Unit 1 — Test 4

The dipole is Oδ−–Cδ+ due to higher electronegativity of oxygen alone.

CO’s bond order is 2.0.

CO has two unpaired electrons in the ground state.

The small dipole moment is oriented Cδ−–Oδ+ because the HOMO is largely carbon‑based.

σ2p below π2p for all.

Levels are identical for all diatomics.

π2p below σ2p for B2–N2, but σ2p below π2p for O2–F2 (due to s–p mixing inversion).

π2p below σ2p for all.

B2 and O2

O2 and O2−

NO and NO+

N2 and O2−2 (peroxide)

Bond order unchanged; only charge changes.

Bond order decreases; bond length increases; two unpaired electrons remain.

O2+ becomes diamagnetic.

Bond order increases; bond length decreases; one unpaired electron remains.

The bonding σ is strongly polarized toward F; the HOMO is a nonbonding F lone pair; LUMO is σ*.

H 1s and F 2p mix equally to give a perfectly covalent bond.

HOMO is on hydrogen; LUMO is H 1s.

The bond is best described as purely ionic H+F−.

It makes N2 paramagnetic.

It is strongest in lighter diatomics (B2–N2), raising the σ2p level relative to π2p.

It equally affects all diatomics.

It is strongest in O2 and F2 and lowers σ2p below π2p.

NO− < NO < NO+

NO < NO+ < NO−

NO+ < NO < NO−

NO+ = NO = NO−

The gap is irrelevant to kinetics.

O2 is inert because it is a triplet.

N2 has a large gap and is kinetically inert; O2 has a smaller gap and is more reactive (despite being thermodynamically stable).

N2 is reactive because it is nonpolar.

H2O: linear with σ and π sets analogous to CO2.

BeH2: bent due to lone pairs on Be.

CO2: linear molecule with degenerate πu and πg sets; symmetric stretch is IR inactive.

O3: linear with degenerate πu and πg sets.