Chemistry Flashcards
Atomic number
of protons, Z
Atomic mass (mass number)
of protons + neutrons, A
Isotopes
Structures of the same element that differ in the number of neutrons
Atomic weight
Weighted average of all isotopes
Plank’s constant
E = hf, h= 6.626 x 10^-34 J·s, Explain’s how matter releases energy as em radiation in quanta
Avagadro’s number
6.6 x 10^23 molecules/mol
Principal quantum number
n, it describes the size of the orbital (energy level). The max # of e- is 2n^2
Azimuthal quantum number
l, the shape and # of subshells. Subshells 0-3 are designated spdf
Magnetic quantum number
ml, the orientation of the orbital within the subshell. This can be between -l and l (max 2 e-)
Spin quantum number
ms, used to distinguish between 2 electrons in an orbital, designated either +1/2 and -1/2. Electrons with different orbitals, but the same spin, are parallel
n+l rule
Used to find what subshell fills first
Hund’s rule
E- fill each subshell before they pair with each other in those subshells (half filled subshells)
Paramagnetic
Elements with unpaired e- (the spin of the unpaired is parallel to each other), IN alignment with magnetic field causing weak attraction
Diamagnetic
Elements with paired e-, repelled by magnetic field, Ex/ wood or plastic
Heisenberg uncertainty principle
Inability to know the position and momentum of a single electron simultaneously. The position is given by the radius of the orbit
Pauli exclusion principle
No two electrons can have the same four quantum numbers or else they would be occupying the same space
Aufbau principle
Electrons will fill lower energy orbitals first before filling higher energy orbitals
*from the German Aufbauprinzip (building-up principle)
Mass defect
Δm = nucleus mass - (mass of protons + mass of neutrons)
Effective nuclear charge (Zeff)
strength of the electrostatic attraction between valence e- and the nucleus (protons). Trend?
Shielding
Valence e- are increasingly separated from the nucleus by inner shells and the outermost e- are held less tightly. This is the effect of the trend for principal quantum number.
Atomic radius
The distance between center of the nucleus and the outermost electron. Decreases from left to right and increases top to bottom (unique trend)
Ionic radius
Half the distance between 2 ions that briefly make contact with each other. Cations will have a larger ionic radius than atomic. Anions will have a smaller ionic radius than atomic
Ionization energy (IE)
energy required to remove an e- from the outer shell of an atom. Endothermic. Completing or disrupting the shell/subshell makes the strength low or high. Trend?
Electron affinity
energy released when an e- is gained. Exothermic. Compare trend to Zeff and atomic radius.
Electronegativity
the attractive force of an element on an e- in a chemical bond. Rlship to IE?
Noble gases
No tendency to gain or lose e-. No measurable electronegativities. Extremely low boiling points. Exist as gas at room temp. London dispersion forces
Transition metals
Conductive and free moving valence e-. Ability to have multiple positive oxidation states from losing e- in their s or d subshells. Form complexes w/ water (hydration) and non-metals.
Metalloids
Can act as both metals and non metals depending on what they are bound to. Semi-conductors.
(8), Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium, Polonium
Ionic bond
bond between an atom of low e- affinity and an atom of high e- affinity. It results from an attraction between opposite charges. Rlship to melting/boiling points?
Covalent bond
an e- pair is shared between 2 atoms. Bond energy and number of e- pairs have an direct rlship.
Dipole moment (p)
p = qd —> q=charge and d=displacement vector. p in Columbs/meter
Coordinate covalent bond
formed when a lone pair attacks an unhybridized p-orbital. Ex/ Lewis rxn
Formal charge (FC)
FC = (Ve-) - (# nonbonding) - (1/2 # bonding)
- the difference between the number of valence e- of an atom in a particular Lewis structure and the number of valance e- normally found in that same atom.
Bent (angle)
104.5 Ex/ H2O
Trigonal pyrimidal
- Ex/ NH3
Tetrahedral (angle)
109.5. Ex/ CH4
Trigonal planar
- Ex/ SO3, CH2O
Trigonal bipyrmidal
90, 120, 180. Ex/ PCl5
Octahedral
90, 180. Ex/ AlF6
London dispersion (van der Waals) forces
weak interactions between a bond and other e- clouds that come within proximity. Rlship to vapor pressure?
Dipole-dipole forces
Direct interaction between 2 magnetic poles. It is an intermolecular force present in solid and liquid phases but negligible in gases
Hydrogen bonds
Occurs in O, N, and F
Equivalent
The amount of acid or base required to produce or consume 1 mole of protons. Describes how many moles of something we are interested in.
Gram equivalent weight
the amount of a compound (measured in grams), that produces one equivalent
GEW = molar mass/n
Normality
measure of concentration given in equivalents/L, commonly used for H+ concentration in acids
Empirical formula
the simplest whole number ratio of the elements in a compound
Molecular formula
the exact # of atoms of each element in a compound
Percent composition
% comp = (mass of element in formula* / molar mass ) x 100
*Assume a 100g when there are unknowns
Combustion reaction
CH4 + 2 O2 —> CO2 + 2 H2O
Limiting reagent
the reactant that has less moles when converted to a product and is used up first
Excess reagent
The reactant that has more moles than the other reactant after being converted into a product
Percent yield
% yield = (Actual / Theoretical) x 100
Rate determining step
Slow step, the rate of the whole reaction is only as fast as this step
Arrhenius reaction
k = Aℇ^(-Ea/RT) A = frequency factor (attempt frequency) which is a measure of how often molecules collide
Activation complex
Energy of the transition state
Exergonic reaction
a negative free energy change, spontaneous
Endergonic reaction
a positive free energy change, non-spontaneous
Factors effecting reaction rate
Concentration, temperature, partial pressure, medium, catalysts (increase forward and reverse rxn)
Zero order reaction
The rate of formation of product C is independent of changes of any of the reactants A and B. Only effected by temp.
Rate = k[A]⁰[B]⁰ = k
First order reaction
The rate is directly proportional to only 1 reactant. Doubling the concentration of that reactant results in doubling the rate of formation of the product
Rate = k[A]¹
Second order reaction
The rate is proportional to either the concentration of 2 reactants OR the square of 1 reactant (Ex/ quartering [A] results in halving the rxn rate)
Rate = k[A]¹[B]¹ or rate = k[A]²
Reaction quotient
indicates how far the reaction has proceeded towards equilibrium by giving the concentrations of reactants and products at a certain point. Rlship to Keq?
LeChatelier’s Principle
If a stress is applied to one side of a system, the system shifts to balance that stress. Rlship to volume, pressure, heat (endo/exo)?
Kinetic product
formed from a reactant at low temperatures with a small heat transfer. Less stable
Thermodynamic product
formed at high temperatures with a large heat transfer. More stable
Kd
Equilibrium constant of the dissociation reaction between receptor and ligand. A smaller Kd = a higher concentration of reactants (receptor-ligand complex) or a higher affinity between receptor and ligand