IB Chem

Elements without an isotope

Fluorine

Differences between isotopes

Chemical properties the same. Physical properties different.

Evaporation vs. Boiling

Evaporation is slow; surface of liquid; no bubbles; leads to cooling; takes place at any temperature

Boiling is fast; throughout the volume; many bubbles; does not lead to cooling; takes place at specific boiling point

Mass spectrometer

Used to determine the relative atomic mass of chemicals. To calculate, you take the data (isotopic masses and their abundance percentages), multiply them by each other, then add them together

Electron Configuration Exceptions

Chromium and Copper.

Electron spin

The way that an electron spins on its own axis. Upward arrow for clockwise, downward for counter-clockwise

Pauli exclusion principle

States an orbital can only hold two electrons of opposite spin

Aufbau principle

That electrons are placed into orbitals of lowest energy first

Hund's third rule

Electrons in the same orbital layer are placed separately to minimize mutual repulsion between them

S-orbitals

sphere shaped. Max 1 (2 e-).

D-orbitals

weird shaped. Max 5 (10 e-).

P-orbitals

dumbbell shaped (figure eight/infinity). Max 3 (6 e-).

F-orbitals

max 7 (14 e-).

Hydrated salt

Compounds with a fixed ratio of water molecules in the crystalline structure

Anhydrous salt

The salt part of a hydrated salt

Hydrated

When molecules are ionized and surrounded by water

Effective charge

The amount of charge which actually attracts outer electrons, as they area shielded by the inner ones. = Protons - Inner shell/core electrons

Allotropes

Different bonding and structural patterns of the same elemnt in the same physical state. Ex. Molecular oxygen (O2) and Ozone (O3)

Diamond

Each carbon bonded to four others. Tetrahedral. Non-electrical conductive, thermal conductive. Transparent, lustrous. Hardest known natural substance, brittle, high melting point

Graphite

Each carbon boned to 3 others. Parallel planes of hexagons. Delocalized electrons and can slide over each other. Conductive of electricity, non-conductive of heat. Non-lustrous, grey. Brittle, high melting point, most stable

Graphene

Each carbon bonded to three others. Two-dimensional hexagons in a single layer. Delocalized electrons. Electrically conductive and most thermally conductive. Almost entirely transparent. Thinnest material to ever exist, strongest to ever exist, flexible, very high melting point. Used in TEM, touch screens, and other electronic devices

Fullerene (C60)

Each carbon bonded to three others. Spherical with pentagons and hexagons. Low thermal and electrical conductivity. Black powder. Light and strong, can react with K to be superconducting, low melting point. Used in lubricants, medical, and industrial devices

Silicone

Elementally bonded to four other silicon in a tetrahedral arrangement. Similar to diamond.

Silicone dioxide (silica, quartz)

Giant covalent tetrahedral structure. Strong, high melting point. Doesn't conduct electricity, insoluble in water. More common than elemental silicone

Biofuels

Fuels produced from the biological fixation of carbon over a short period of time. Renewable and sustainable. Ex. Photosynthesis creating glucose

Gasohol

A mixture of 10% ethanol and 90% unleaded gasoline.

Advantages of biofuels

Cheap and available. Renewable and sustainable. Less polluting than fossil fuels.

Disadvantages of biofuels

Uses land. High cost of harvesting and transportation. Takes nutrients from soil. Lower specific energy than fossil fuels.

Fuel cell

Where reactants are continuously supplies to electodes to produce electricity

Hydrogen fuel cell

Uses hydrogen and oxygen gas as reactants to release energy. Porous carbon with a transition metal as inert electrodes.

Cons of hydrogen fuel cell

Hydrogen gas is almost never found in nature. Extracting it from hydrocarbons, fossil fuels, and biomass gets hydrogen but also carbon dioxide. It can also be extracted through electrolyzing water, but… if we had the energy we wouldn't be in this situation.

Direct methanol fuel cell (DMFC)

Methanol is oxidized under acidic conditions on a catalyst surface to form carbon dioxide. H+ ions are transported across a proton exchange membrane from anode to cathode, with electrons transported through an external circuit from anode to cathode, reacting with oxygen to produce water. Water is consumed at the anode and produced at the cathode

Quenching

Where a substance is introduced to stop the reaction at the moment it is withdrawn to get a specific time.

Maxwell-Boltzmann Energy Distribution Curve

Shows the number of particles with kinetic energy vs. the amount of kinetic energy they hold in a gas

Amphoteric

Substances that can both donate and receive electrons. Includes amphiprotic

Amphiprotic

Substances that can act as a bronsted-lowry acid and base in different reactions

Effervescence

When reactions involve a gas and produce bubbles

What is a radical

A chemical species that contains an unpaired electron. High enthalpy, very reactive, don’t exist long outside of the upper atmosphere, can break bonds in otherwise stable molecules

Radicals

Cl, Br, H, Nitric Oxide, Hydroxyl radical, methyl radical, superoxide radical, benzene radical anion, propane cation, ethanol cation

Homolytic fission

When a covalent bond breaks to form two radicals, with both products having an equal assignment of electrons from the bond

Thermolytic fission

Homolytic fission by heating the compound, for weaker bonds

Photolytic fission

Homolytic fission through high-energy UV light, for stronger bonds

Chlorofluorocarbons

When entering the stratosphere, are broken down to release reactive chlorine radicals. C-Cl bond breaks before C-F because it has lower bond enthalpy.

Radical substitution reactions

When formed from alkane substitution, start a chain reaction form a halogenoalkane. Intiate (usually photolytic fission); propagate (react with other species to form new radicals); terminate (form covalent bonds, revers homolytic fission, gets rid of radicals)

What is a Nucleophile

A reactant that forms a coordination covalent bond to its reaction partner by donating bonding electrons

Neutral nucleophiles

water, ammonia, alcohols, amines

Charged nucleophiles

hydroxide, F-, Cl-, Br-, I-, CN-, R-

Electrophile

The nucleophile's bonding partner, forming a covalent bond by accepting bonding electrons. Note that not all molecules are electron deficient, but can act as electrophiles in addition reactions (e.g. Br2)

Neutral electrophiles

hydrogen halides, halogens, halogenoalkanes, water (neutral)

Charged electrophiles

Carbocations, H+, NO2+, NO+, CH3+

Continuous Spectrum

A spectrum that contains all wavelengths of light, produced when white light is passed through a prism

Line Spectrum

A range of emissions of light, sound, or other radiation

Emission Spectrum

Shows coloured lines of emission from a glowing gas (shows what is emitted). When atoms move from a higher energy state to a lower energy state, and a photon of a specific energy level/frequency are emitted. Converge at higher energies

Absorption spectrum

Shows black lines where light does not pass through (shows what is absorbed). When atoms absorb energy, moving from a lower to higher energy level

Ionization energy

The amount of energy needed to remove an electron from the ground state of a mole of gaseous atoms, ions, or molecules

Ionization energy trends

Metals on the left and bottom of the periodic table have lowest ionization energies and thus form positive ions most readily. Non-metals on the right and top of the table have highest ionization energies and thus form negative ions more readily.

Ways to separate a mixture

Distillation, filtration, evaporation, chromatography, decantation

Decantation

Pouring a liquid from a solid

Energy level

Main shells/principal quantum number (n)

Sublevels

Divisions within energy level shells (s, p, d, f)

Orbitals

Specific regions in sublevels where electrons are most likely to be found

Ultraviolet-visible spectroscopy

Uses the direct relationship between the concentration of a solution and its absorbance

Calibration

The graphed absorbance of each solution concentration, used to determine the unknown concentration of a sample with the same solute

Sulfate (formula, charge, acid)

SO4(2-) sulfuric acid

Nitrate (formula, charge, acid)

NO3(-) nitric acid

Phosphate (formula, charge, acid)

PO4(3-) phosphoric acid

Hydroxide (formula, charge, acid)

OH(-) water

Hydrogencarbonate (formula, charge)

HCO3(-)

Carbonate (formula, charge, acid)

CO3(2-), carbonic acid

Ammonium (formula, charge)

NH4(+)

Lattice enthalpy

The enthalpy change in the process of reversing an ionic, lattice bond

Avogadro's law

Equal volumes of gases, measured at the same temperature and pressure, contain equal numbers of particles. For ALL gases. Based on the ideal gas model (1.5)

Axioms for ideal gas law

Particles of gas have negligible volume compared to the volume the gas has. There are no significant intermolecular forces when molecules aren't colliding. Gas particles have a range of speed and move randomly with average kinetic energy proportional to temperature. Elastic collisions

Real gases

If particle volume isn't negligible, increased collisions and pressure. If attractive forces are greater, lower speeds and pressure.

When do real gases act like ideal gases?

Low pressure high temperature

Units for ideal gas law (pressure, volume, temperature)

kPa or atm, m^3 or cm^3 or dm^3, K

Electronegativity

A measure of the ability of an atom to attract electrons to the bond

Ionic character

Calculated with electronegativity difference divided by CsF electronegativity difference (most ionic, 3.2)

Bonding continuum compound numbers

Greater than 1.8 ionic; less than 1.8 covalent

Ways to compare bond strength

Lattice enthalpy (stronger = negative), ionic charge (stronger = large), ionic radius (strong = small)

Why not to use ionic character for bond strength

It is tendency to form an ionic bond, not strength

Atoms which do not use the octet rule

B (6) and Be (4)

Bond strength

energy required to break a bond, described in terms of bond enthalpy

Bond length vs strength and relation to atomic radius

Longer bonds = weaker strength, longer bonds with larger atomic radius

Linear bond

Two other atoms, no lone pairs. CO2. Symmetry determines polarity. 2d, 180 degrees.

Trigonal planar bond

Three other atoms, no lone pairs. BH3. Symmetry determines polarity. 2d, 120 degrees.

Tetrahedral bond

Four other atoms, no lone pairs. CH4. Symmetry determines polarity. 3d. 109.5 degrees.

Pyramidal bond

Three other atoms, lone pair. NH3. Always polar or slightly. 2d, 104 degrees.

Bent bond

Two other atoms, lone pair. H2O. Polar or semi-polar. 3d, 107 degrees.

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Catenation

Tendency of atoms to bind to others of the same type in a chain. Such as C-C.

Thin layer chromatography

Stationary phase is a layer of silica or aluminum oxide on glass, metal, or plastic. Surface contains OH to form H bonds with the sample.

Metallic bonding

Where electrostatic attraction between lattice of cations and delocalized electrons in metal molecules causes formation of a lattice structure.

Strength of metallic bonding

Number of delocalized electrons (more), charge, and radius of the cation (less)

Metallic properties

Conductive because of delocalized electrons. Thermally conductive because of close packing and delocalized electrons. Malleable and ductile because delocalized electrons are non-directional, keeping bonds intact when conformation changes. High melting point because of the strong attraction. Shiny, lustrous appearance because delocalized electrons reflect light

Alloys

Homogenous mixtures containing at least one metal held together by metallic bonding. Makes them stronger because different sizes prevent slipping of atoms across each other. No fixed composition and cannot be represented by a formula.

Example of an alloy

Iron + carbon makes steel, high tensile strength but corrodes. Used as a structural material.

Recyclable

A substance that can be processed chemically into a new product

Biodegradable

Substance that will be broken down in the natural environment into harmless products

Reusable

Can be reused without physical or chemical change