Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Psych 251 > Chem 225 > Flashcards

Chem 225 Flashcards

You may prefer our related Brainscape-certified flashcards:
Psychology 101 flashcards GRE® Psychology flashcards
1
Q

symmetry elements/operations

A

Describe specific symmetry relationships between areas within an object.
Examples: rotation axis, plane of symmetry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

point group

A

A collection of symmetry elements that describes the overall symmetry of an object. All point groups include the identity element E.
Examples: C2v, C2h , Td, Oh

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

irreducible representations

A

A set of characters within a Character Table describing a mathematically allowed sub-symmetry of the point group.
Examples: within C2v, 1, -1, 1, -1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

characters

A

Positive or negative values within an irreducible representation (within a Character Table), referring to symmetric, antisymmetric, or asymmetric with respect to a symmetry element.
Examples: 0, 1, -1, 2, -2, 3, -3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Identity element, E

A

Present in all point groups with a positive character of 1, 2 or 3. The identity operation does not move the object (molecule), and is present for mathematical reasons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Rotation axis, Cn

A

Symmetry with respect to a partial rotation around a central axis that passes through the object. n is an integer that defines the ‘fold’ of the
rotation, which is the number of turns to complete 360°, i.e. 2 (180° each), 3 (120° each), 4 (90° each), 5 (72° each), 6 (60° each), etc.
- For objects with more than one axis of symmetry that are perpendicular, the axis with the highest fold is referred to as the principal axis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Plane of symmetry, σ

A

symmetry with respect to a plane through the center of the object. A plane that includes the principal axis is labelled σv and a plane that is perpendicular to the principal axis is
σh.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Center of inversion, i

A

symmetry with respect to a combination of a C2 and σh. Inversion of all components of the molecule through the center of the molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Improper axis, Sn

A

Symmetry with respect to a combination of a fraction of a rotation Cn (n is greater than 2) and reflection through a perpendicular plane.
Example in red is S 4, 90° rotation about
the C 2 and reflection through the
perpendicular plane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

cubic close packing (ccp)

A
  • ABCABC
  • packing of hexagonal 2D layers
  • also known as face centered cubic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

hexagonal close packing (hcp)

A
  • ABAB
  • packing of hexagonal 2D layers
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

non close-packed arrays

A
  • Simple cubic lattice and body-centered cubic
  • These are the simplest lattices
  • Both are built from square 2D packed
    layers
  • They differ only by whether alternate layers are placed in “holes” or directly over the previous layer’s
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Effect of temperature of metals and semiconductors

A
  • Semiconductors: the temperature dependence of the number of mobile electrons is more important
    than the temperature dependence on lattice vibrations. As a result the resistivity of decreases with increasing temperature
  • Metals: the temperature dependence of resistivity is determined by the lattice vibrations. As a result the resistivity increases with increasing temperature
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

1:1 structures

A
  • Rock salt (NaCl) structure: fcc (ccp) lattice for both Na+ and Cl-. Many other salts have the same structure, need a 1 to 1 stoichiometry
  • Cesium chloride: simple cubic lattice, salts containing large cations. Octahedral holes in close-packed anion structure only have room for cations 41% of anion size. So this adopts a non-close packed structure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

1:2 structures

A
  • Fluorite (CaF2): a face-centered cubic lattice of Ca2+ ions with F- in all tetrahedral holes
  • Zinc blended: Only half the tetrahedral holes filled. Preferred coordination number of 4
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Oxidation vs. reduction

A

Oxidation: Loss of electrons of the reducing agent
Reduction: Gain of electrons of the oxidizing agent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Galvanic cells vs. electrolytic cells

A
  • In electrolytic cells, the passage of electrical current causes a chemical reaction to occur whereas in a Galvanic (or Voltaic) cell, a spontaneous chemical reaction causes electrons to flow
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Hydrogen compounds

A
  • ionic hydrides (E+H-): True ‘saline’ (ionic) hydrides only form with groups 1 and 2
  • covalent hydrides
    -hydridic: H slightly - , polymeric solids, electron bridging, BeH2, B2H6, MgH2, SiH4, SnH4, etc
    • neutral: CH4, PH3, AsH3
    • protic: H slightly + , high Bp gases or liquids, NH3, H2O,H2S, HX
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Uses of hydrogen

A
  • Fuel cells, energy storage
  • Chemical synthesis (e.g. addition to double bonds w/ catalyst)
  • Reduction of salts to metals instead of C ( e.g. MoO3 + 2H2 → Mo + 3H2O )
  • Used in synthesis of ammonia by the Haber-Bosh process
20
Q

Group 1: Alkali metals

A
  • Silvery, low melting metals by electrolysis of molten salts
  • Form mostly soluble salts that are powerful reductants and very reactive as a result
  • Dissolved in liquid NH3 to form ‘solvated electron’ solutions
21
Q

Flame tests for group 1 metals

A
  • Atomic emission spectra
  • Li: crimson, Na: yellow, K: purple, Rb: red-violet, cesium: blue
22
Q

Group 1 uses

A
  • Lithium ion batteries: Rechargeable, High energy density, Used in portable electronics, flammable (e.g. LiC6, lithium graphite)
  • LiC6: INTERCALATION COMPOUND
  • Organolithium reagents: C-C bond formation (similar to, but more reactive than, Grignard reagents, RMgX)
    • M-C bond formation
    • Anionic polymerization initiator (e.g. styrene to polystyrene)
23
Q

Group 2: Alkaline earth metals

A
  • Silvery metals, higher mp than group 1, less reactive bc harder to oxidize due to increasing Zeff.
  • reactivity with water: M= Mg &laquo_space;Ca, Sr< Ba
24
Q

Group 2 uses

A
  • MgO: A REFRACTORY MATERIAL= Very high mp, insulator, not ‘workable’
    • Ceramics, or oven/furnace liners
  • Calcium: limestone (CaCO3) is ‘calcined’ with heat to make lime/quick lime CaO, with water it becomes ‘slaked’ lime Ca(OH)2
  • Calcium carbide (CaC2): formed from carbon and CaO at high temperatures, hydrolysis releases acetylene gas. Used in miners lamps
25
Q

Group 13: metals and non-metals

A

exemplifies almost all periodic trends:
- change from covalent (B) to ionic bonding (Al down) = Decreasing Q/r ratio
- nonmetal (B) and metal behaviour (Al down) = Decreasing Q/r, more orbitals
- diagonal relationships (B →Si and Be →Al) = Similar Q/r: increased charge
offsets increasing size

26
Q

inert pair effect

A

s-electrons have electron density near the nucleus and the very high Z means electrons experience an increase in mass if close to the nucleus - a relativistic effect. This lowers the s-electron energy enough that it takes too
much energy to remove them, i.e. they become ‘inert’
Ex: Oxidation states: +3 for most but heaviest member Tl dominated by +1.

27
Q

Where and how aluminum metal

A
  • Most abdundant metal in Earth’s crust
  • Huge energy cost to mine
  • Prepared by electrolysis (Hall-Héroult Process)
  • Al2O3 (Na3AlF6 ) + 2C (s) → 2 Al (l) + CO (g) + CO2 (g)
28
Q

Aluminum hydroxides and oxides

A
  • Dissolves in acids or bases: amphoteric
  • Conversion of hydroxides to oxides is condensation (- H2O)
  • Al2O3 and B2O3 is like quartz
  • SiO2 (silica) and borosilicates are similar to pyrex
29
Q

Boranes and boric acid

A
  • Boranes: B/H compunds
  • Types: Arachno (Web, B4), Nido (Nest B5) and Closo (cage, B6 or C2B4)
  • Boric acid: B(OH)3, weak acid (pKa 9.5), extensive hydrogen bonding in a sheet structure, used as a mild antiseptic: eye/mouth wash
30
Q

Group 14

A
  • group includes non-metals (C), semi-metals (Si, Ge) and metals (Sn, Pb)
  • all elements catenate to some degree
  • inert pair effect for Sn and especially Pb (2+ state is important)
31
Q

Allotropes of carbon

A
  • Graphite (sp2): conductor
    • Very soft: layers can slide over one another. Intercalation compounds: e.g. C6K
  • Diamond (sp3): insulator
    • Extremely hard, must break several bonds to move C atoms
  • Graphenes (sp2):
  • Fullerenes
  • Nanotubes
32
Q

Silicones/siloxanes uses

A
  • Produced on a massive scale
    industrially
  • Low toxicity and cheap leads
    to many uses:
  • Oil baths, hydraulic fluids (stable to many chemicals and high T)
  • Personal care products as lubricants: shampoo, conditioner, antiperspirant, hair gels, toothpaste, shaving cream
  • Greases, sealants, gaskets
  • Medical implants
33
Q

Group 15: pnictogens

A
  • non-metals except for Bi
  • tend to catenate
  • multiple bonding rapidly declines down the group:
  • N≡N bond strength (942 kJ/mol) is >50% stronger than 3 times the N-N bond strength (600 kJ/mol)
  • P≡P bond strength (480 kJ/mol) is 30% less than 3 times the P-P single bond energy (630 kJ/mol)
34
Q

Arsenic compounds

A
  • Bind strongly to S and disrupts S-S bonds
  • Poisonous: Napoleon was poisoned with As – deliberately or not!
  • Strong antibacterial properties
  • Ehrlich’s Magic Bullet: Developed the cure for Syphilis. Originator of chemotherapy
35
Q

Group 15 pesticides and nerve agents

A
  • Pesticides: Parathion, diazinon, malathion (the safest)
  • Nerve agents: Sarin and soman
    • Mechanism: Acetylcholine esterase (ACE) inhibitors – interfere with the ‘off’ switch leading to uncontrolled nerve impulses and death
36
Q

Group 16: chalcogenides

A
  • Oxygen: O2 or O3 gases, insulator, pπ-pπ bonding, very little catenation, strong oxidizing ability
  • Sulfur: S8 and many other Sn, insulator, bonding mainly with O, extensive catenation, weak oxidizing ability
  • Selenium: Sen helical chains, semiconductor, no multiple bonding, significant catenation, no oxidizing ability
    Tellurium: Ten helical chains, semiconductor, no multiple bonding, significant catenation, no oxidizing ability
37
Q

Group 16 catenation

A
  • Sulphur has the 2nd greatest tendency to catenate after carbon
  • S8: yellow sulfur, S chain: red liquid, cooled: black plastic sulfur
  • But…many other catenation compounds of S, Se, and Te are known
  • MoS2 (lubricant) and FeS2 (Fool’s gold) contain S2 2- anions
38
Q

Group 16: selenium and tellurium

A
  • Se and Te are photosensitive semiconductors: they conduct when exposed to light
  • The Xerox process: old printing method using a selenium-coated drum and charge
39
Q

Sulfur oxides

A
  • Combustion of any S-containing material (especially coal) produces SO2 (g)
  • SO2 slowly converts to SO3 which dissolves in water to form H2SO 4 (part of acid rain):
    • degrades limestone used in buildings
    • limits ability of freshwater to support fish/plants
  • But, SO2 can be useful:
    • Used in bleaching of wood pulp in pulp+paper industry
    • Antibacterial sprayed on fruit or added to wine as a preservative: dissolves in
      water and converts to sulphite (SO32-) salts
40
Q

Group 17: halogens

A
  • Fluorine: only -1 valence in compounds, weak F-F bond (extreme lone pair repulsion), reacts with virtually all elements (except N and O), extremely oxidizing, Eº = +2.87V, very strong and unreactive C-F bonds, e.g. teflon
  • Chlorine: yellow gas, Eº = +1.36V, PVC, other polymers, bleach (ClO -), solvents
  • Bromine: red liquid, Eº = +1.09V, Photographic film, flame retardants
  • Iodine: purple solid, Eº = +0,54V, disinfectant, X-ray contrast agent, catalysts
41
Q

Stereoisomers and types

A
  • Stereoisomers: same chemical formula, same bonds but different relative orientation of those bonds
  • Enantiomers: Mirror image, same physical
  • Diatereomers: Non mirror images, different physical properties (ex: cis vs trans or mer vs. fac)
42
Q

Strucral isomers and types

A
  • Structrual isomers: same formula, different atom connectivity
    1. Ionization isomers: interchange of an anionic ligand in 1st coordination sphere with anion outside the coordination sphere
    2. Hydration isomers: interchange another ligand in 1st coordination sphere with outer sphere water
    3. Coordination isomers: interchange of ligands in first coordination spheres of salt where both cation and anion are coordination complexes
    4. Linkage isomers: same ligand bonded to the metal in different ways (an ambidentate ligand)
43
Q

π donors vs. π acceptors

A
  • π donors: ligand with filled π orbitals, greater M character in anti-bonding, greater L character in bonding, weak field, smaller delta o
  • π acceptors: ligand with empty π orbitals, greater L character in anti-bonding, greater M character in bonding, strong field, larger delta o
44
Q

Generalizations about delta o

A

1) For a given M n+ ion, the position of L in the spectrochemical series predicts the magnitude of delta o
2) For a given ML6 with M in different oxidation states: the higher oxidation state has the higher delta o
3) For a given MLn in a single triad: heavier metal has the higher delta o
4) BUT, there is NO TREND in delta o across the series for different M with the same ox. state and ligand set

45
Q

Types of radio active decay

A
  • Beta (β) radiation involves emission of high-speed electrons. Neutron converts to proton + ejected e-
  • Gamma (γ) radiation involves emission of a very short wavelength (high energy) photon. It usually accompanies other radioactive decay because it represents the energy lost when the nucleus changes into a more stable arrangement
  • Positron emission involves an anti-electron being generated. Proton converts to neutron + ejected positron
  • When a positron encounters an electron, they annihilate each other and produce two gamma rays
  • Electron capture involves a nucleus capturing an orbital electron. Electron is captured and combines with a
    proton to give a neutron
46
Q

N and Z ratios in stability belt

A
  • Z ≥ 84 decay by alpha emission (decreases both N and Z)
  • High N/Z ratio nuclides usually decay by beta-emission (Nˇ, Zˆ)
  • Low N/Z ratio nuclides usually decay positron emission or electron capture (Nˆ, Zˇ)

Psych 251 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions