U3 E&S Flashcards
Explain the relationship between wavelength and energy.
The shorter the wavelength, the more energy is released. (Gamma rays have high energy, whereas radio waves release lower amounts of energy).
In other words, energy is inverse to wavelength.
Differentiate between an emission spectrum, a continuous spectrum, and a line spectrum.
Emission: collection of coloured lines produced when light is shone through diffraction grating or a spectroscope. (Bohr)
Continuous: basically the entire colour spectrum. Contains all wavelengths of light.
Line: (fingerprint) made of a collection of discrete lines unique to each element.
What is Planck’s constant?
6.63 x 10^-34
How do we calculate IE1 (first ionization energy)?
IE1 = hc / λ
h = Planck’s c = speed of light (3 x 10^8 m/s) λ = wavelength
Define “First Ionization Energy” and state its general equation.
The amount of energy required to move 1 mol e- from the ground state of 1 mol gaseous atom.
ADD GENERAL EQUATION
Explain the general trend of IE in the periodic table.
IE increases to the right and down:
- effective nuclear charge means more protons along a period but uniform energy shell
- shielding effect of inner energy level electrons
What is Bohr’s explanation of the atom?
- Electrons surround nucleus in energy levels of orbitals
- Ground state = lowest possible energy level(s)
- Electrons + energy = jump to higher levels
- Electrons descending E levels = “quantized” energy given off (small discrete indivisible quantity of light)
- each line in line (atomic) spectrum corresponds to a transition from high to low
- larger the transition, greater the E released
- limited # transitions possible for e- to follow, hence the fingerprint-like line spectrum (specific frequencies)
Define “effective nuclear charge”.
Protons have a strong hold on electrons. In IE graphs, the electrons in the outermost energy levels have a less effective nuclear charge than those on the innermost energy levels. Effective nuclear charge increases to the right and down on the periodic table.
How do you deduce the group # of an element from the IE’s?
Deduce group number by looking at any massive JUMPS between IE values (ex. Massive jumps between 1450kJ/mol and 7750kJ/mol suggest removal of an e- from an orbital CLOSEST TO THE NUCLEUS.)
How does the trend in IE account for irregularities in an IE graph?
When a graph is drawn in a jagged pattern (IE increases, decreases, then increases again) then this could indicate electrons being removed from the [4s] orbital, then the [3p] orbital, then the [3s] orbital, etc…
Describe the structure, bonding, appearance, conductive properties, special properties, uses and hybridization of GRAPHITE.
Structure: hexagons in parallel layers, 2D
Bonding: C’s connected to 3 other C’s, bond angle < 120°, held by weak Lond. Disp. forces so can slide overtop one another (layers) - Sp2 hybridized
Electrical conductivity: good, 1 non-bonded e- per atom so gives mobility.
Thermal conductivity: not good (unless heat can be forced to conduct in direction parallel to crystal layers)
Appearance: non-lustrous, grey crystal solid
Special properties: soft/slippery layers, brittle, v. high mp, most stable C allotrope
Uses: dry lubricant, pencils, electrode rods in electrolysis
Describe the structure, bonding, appearance, conductive properties, special properties, uses and hybridization of DIAMOND.
Structure: 3D crystal lattice structure of C atoms
Bonding: C cov. bonded to 4 others, bond angle < 109.5° - Sp3 hybridized
Electrical properties: non-conductive, all e’s bonded (not mobile)
Thermal properties: effective thermal conductor, better than metals.
Appearance: highly transparent lustrous crystal
Special properties: hardest allotrope, cannot be scratched, brittle, v. high mp
Uses: jewellery, tools to grind/cut glass
Describe the structure, bonding, appearance, conductive properties, special properties, uses and hybridization of FULLERENE C60 (Bucky Balls).
Structure: ball-like structure w/ fixed formula
Bonding: C’s bonded in sphere of 60, 12 pentagons and 20 hexagons, closed cage in which each C is bonded to 3 others (finite) - Sp2 hybridized
Electrical conductivity: semi-conductor @ normal temp./press. due to some e- mobility (easily accepts e-‘s to form -ve ions)
Thermal conductivity: v. low thermal conductivity
Special properties: v. light and strong, reacts with K to make superconducting crystal material, low mp
Uses: medical/industrial devices for binding specific target molecules, nanotubes, can act as catalysts
Describe the structure, bonding, appearance, conductive properties, special properties, uses and hybridization of GRAPHENE.
Structure: single-layer and 2D allotrope of C in sheets (hexagons, so honeycomb or chicken wire)
Bonding: C atom bonded to 3 others, bond angle < 120° - Sp2 hybridized
Electrical conductivity: good electrical conductor, one delocalized e- per atom (mobility)
Thermal conductivity: most thermally conductive!!! Even better than diamond
Appearance: almost transparent (given its 1 atom thickness)
Special properties: strongest (100x than steel), v. flexible, v. high mp
Uses: transmission electron microscopy (TEM), photo-voltaic cells, touch screens
Explain why the M3+ ion is more stable in d-block elements Sc to Cr but the M2+ ion is more common in the elements thereafter?
Effective nuclear charge makes it harder to remove the electrons from the orbitals from Mn to Zn
