Structure and Properties of Matter: Unit Review

Most alpha particles passed straight through (mostly empty space); a very few bounced back, which showed a tiny, dense, positive nucleus.

The plum pudding model: electrons in a sphere of positive charge. Cathode rays bent towards a positive plate and had the same charge-to-mass ratio for every metal.

1.0 × 10⁻¹⁰ ÷ 2.0 × 10⁻¹⁵ = 5.0 × 10⁴ times.

E = hc/λ = 1.9878 × 10⁻²⁵ ÷ 5.00 × 10⁻⁷ = 3.98 × 10⁻¹⁹ J.

ΔE = 2.18 × 10⁻¹⁸(1/4 − 1/25) = 2.18 × 10⁻¹⁸ × 0.21 = 4.578 × 10⁻¹⁹ J. λ = 1.9878 × 10⁻²⁵ ÷ 4.578 × 10⁻¹⁹ = 4.34 × 10⁻⁷ m = 434 nm (violet).

Electrons have only certain energy levels, so only certain energy differences (photon energies) are possible.

λ = 6.626 × 10⁻³⁴ ÷ (9.11 × 10⁻³¹ × 5.0 × 10⁶) = 6.626 × 10⁻³⁴ ÷ 4.555 × 10⁻²⁴ = 1.45 × 10⁻¹⁰ m.

An orbit (Bohr) is a fixed circular path; an orbital (quantum model) is a 3-D region where the electron is likely to be found.

The exact position and momentum of an electron cannot both be known at the same time.

No: for l = 1, mₗ can only be −1, 0 or +1.

16 orbitals, 32 electrons.

A 4f orbital.

[Ar] 4s² 3d¹⁰ 4p⁴.

Mn = [Ar] 4s² 3d⁵; Mn²⁺ = [Ar] 3d⁵, 5 unpaired electrons.

[Ar] 4s¹ 3d⁵: a half-filled d sublevel is especially stable, and 4s and 3d are close in energy.

[Ar] 4s²: all paired: diamagnetic.

p block; 5s² 5p².

Aluminium's outer electron is in a 3p orbital, higher in energy and shielded by 3s, so it is easier to remove.

Any two: ions of several charges, coloured compounds, paramagnetism, catalytic activity, high melting points.

AX₃E: trigonal pyramidal, angle a little under 109.5° (about 94° measured; accept "less than 109.5°").

3 electron groups on N, no lone pairs: trigonal planar, 120°.

O in water has 2 lone pairs (4 groups, AX₂E₂); C in CO₂ has 2 groups and no lone pairs.

AX₄E: seesaw.

AX₄E₂: square planar, 90°.

S is in period 3 and can have an expanded valence shell; O (period 2) has only four valence orbitals and is small.

CO₂: sp; CH₃OH: sp³.

σ: 4 C–H + 2 C–C = 6 σ; 2 π.

Side-by-side p-orbital overlap is less effective than end-to-end overlap.

Yes: tetrahedral but with two kinds of outer atom, so the C–F dipoles are not cancelled.

No: trigonal planar with three identical B–Cl dipoles that cancel.

It must be symmetrical (with identical outer atoms) so the bond dipoles cancel.

London dispersion, dipole-dipole and hydrogen bonding.

propane < methoxymethane < ethanol.

Br₂ has more electrons, so its London forces are stronger.

Propanone: weaker IMFs (no hydrogen bonding between its molecules).

Adhesion to the polar glass is stronger than cohesion, and surface tension pulls the column up: capillary action.

Air pressure is lower, so water's vapour pressure equals the surrounding pressure at a lower temperature.

(a) ionic (b) covalent network (c) metallic (d) molecular.

Metal layers slide but the electron sea keeps holding the cations; in an ionic crystal a shift brings like charges together and they repel.

K (metal) + Br (non-metal): ionic (KBr).

Covalent network.

To show the water itself does not conduct, so any current comes from the sample.

Example: unequal amounts heated for different times; use equal masses side by side on one surface for the same time (or use a melting-point apparatus).

Radio signals from hydrogen nuclei (spin) in a magnetic field; it uses no ionizing radiation.

A C=O (carbonyl) group.

Any two: Gillespie (VSEPR), Herzberg (molecular spectroscopy, 1971 Nobel), Rutherford (nuclear atom; radioactivity work at McGill), Brooks (radioactivity), Bader (atoms in molecules), Polanyi (reaction dynamics, 1986 Nobel), Brockhouse (neutron scattering, 1994 Nobel), Strickland (laser pulses, 2018 Nobel).

Rigid, aligned polymer chains held together by many hydrogen bonds between C=O and N–H groups.

Its critical temperature (about 93 K) is above liquid nitrogen's boiling point (77 K).

Example: ZnO nanoparticles in sunscreen block UV while clear; their effects in waterways are still being studied.