General and Organic Chemistry Flashcards
Atoms
tiny particles that makes up all mass
nucleus
consists of protons and neutrons which are collectively called nucleons
Strong nuclear force
force that holds protons and neutrons together
Binding energy
the energy that would be required to break the nucleus into individual protons and neutrons; a measure of the stability of the nucleus
Proton
positively charged, same mass as neutron but much greater than electron
Neutron
neutrally charged, same mass as proton but much larger than electron
Electron
negatively charged, much smaller than proton and neutron
Element
building blocks of compounds and cannot be decomposed into simpler substances by chemical means
Atomic number
indicates the number of protons and provides the identity of the element
Mass number
number of protons plus neutrons
Atomic weight
molar mass; units of amu (atomic mass unit or g/mol)
Isotopes
two or more atoms of the same element that contain different number of neutrons
Ion
when then number of electrons in an atom does not match the number of protons and so the atom carries a charge
Cation
positively charged ion, smaller than neutral compound
Anion
negatively charged ion, larger than neutral compound
Periodic table
lists the elements from left to right in order of their atomic number
Period
horizontal row of periodic table
Group/family
vertical column of periodic table; elements in the same group share some similar chemical and physical properties
Metals
large atoms that tend to lose electrons to form positive ions and positive oxidation states; have a loose hold on their outer electrons which causes their characteristics: lustrous, ductile, malleable, and thermally and electrically conductive
Nonmetals
form covalent bonds with one another and generally speaking have lower melting points than metals; tend to form anions
Metalloids
have some metallic and some non-metallic characteristics
Representative elements
groups 1-2, 13-18; make ions by forming the closest noble gas electron configuration
Transition metals
groups 3-12, can form multiple ions with various charges
Elements with half filled or filled orbital
groups 1-2: half-filled and completely filled s orbitals; groups 7 and 12: half-filled and completely filled d orbitals; groups 15 and 18: half-filled and completely filled p orbitals `
Valence electrons
electrons in the outermost shell; contribute most to an element’s chemical properties; in most cases, only electrons from the s and p subshells are considered valence electrons
Alkali metals
Group 1 metals; soft metallic solids with low densities and low melting points that easily form 1+ cations; highly reactive with nonmetals to form ionic compounds and react with H to form hydrides; react exothermically with H20 to produce metal hydroxide and H2 gas
Alkaline earth metals
Group 2 metals; harder, more dense, and melt at higher temperatures than alkali metals; form 2+ cations and are less reactive than alkali metals because their highest energy electron completes the s orbital
Oxygen group/chalcogens
know oxygen and sulfur; oxygen is 2nd most electronegative element, it is divalent and can form strong pi bonds to make double bonds; typically reacts with metals to form metal oxides; akali metals form peroxides and super oxides; sulfur can form many more bonds than oxygen because it has access to the 3d orbital; S also has ability to form double bonds
Halogens
F, Cl, Br, I; highly reactive; like to gain electrons; react with metals to form ionic halides; can combine with hydrogen to form gaseous hydrogen halides which are soluble in water, forming hydrohalic acids
Noble gases
inert gases that nonreactive
Atomic radius
distance from the center of the nucleus to the outermost electron
Atomic radius trend
increases moving down a group and across a period from right to left
Electrostatic force
the force between charged objects following coulomb’s law F = kq1q2/r^2
Effective nuclear Charge (Zeff)
the amount of charge felt by the most recently added electron
Zeff trend
increases going left to right and from top to bottom
Ionization energy
the energy needed to detach an electron from an atom
First ionization energy
the energy necessary to remove an electron from a neutral atom in its gaseous state to form a +1 cation
Second ionization energy
the energy required for the removal of a second electron from the same atom to form a +2 cation; always greater than the first ionization energy
Ionization energy trend
increases along the periodic table from left to right and from bottom to top
Electronegativity
the tendency of an atom to attract electrons shared in a covalent bond
Electronegativity trend
increases from left to right and from bottom to top
Electron affinity
the willingness of an atom to accept an additional electron
Electron affinity trend
increases from left to right and from bottom to top
Quantum mechanics
elementary particles can only gain or lose energy in discrete units
Bohr atom
represents the atom as a nucleus surrounded by electrons in discrete electron shells
orbital structure of the H atom
a single e- orbits the hydrogen’s nucleus in an electron shell
Pauli Exclusion Principle
no 2 electrons in the same atom can have the same 4 quantum numbers
Principal quantum number, n
the first quantum number which designates the shell level of the electron, with low numbers closest to the nucleus
Subshell, L
shape of orbital; L= 0 is s subshell, L =1 is p subshell etc.; range from 0 to n-1
Magnetic quantum number, Ml
specific orbital within a subshell, value from -L to L
Electron spin quantum number, Ms
distinguishes between 2 electrons in the same orbital; one is spin +1/2 and the other is spin -1/2
Heisenberg Uncertainty Principle
there is an inherent uncertainty in the product of the position of a particle and its momentum; xp >= h/2
Aufbau principle
with each new proton added to create a new element, the new electron is added to maintain neutrality will occupy the lowest energy level available
Exceptions for electron configuration
Elements in Group 6 (Cr) and Group 11 (Cu), borrow 1 electron from the highest s subshell so they end up with a half-filled s subshell and a half-filled or filled d subshell
Electron configuration
lists the shell and the subshells of an element’s electrons in order typically from lowest to highest energy level
Ground state
lowest energy level
Excited state
when at least one e- has moved from a lower energy subshell to a higher energy subshell
Hund’s rule
electrons will not fill any orbital in the same subshell until all orbitals in that subshell contain at least one electron and that the unpaired electrons will have parallel spins
Paramagnetic elements
elements with unpaired electrons that align with an external magnetic field
Diamagnetic elements
elements with no unpaired electrons and are unresponsive to an external magnetic field
Emission line spectrum
spectrum that is characteristic of a given element from energy released when excited electrons fall from a higher energy state to a lower energy state
Absorption line spectrum
measures the radiation absorbed when electrons absorb energy to move to a higher energy state
Photoelectric effect
the emission of electrons when light falls on a material; KE = hf - work function
Covalent bond
electrons are shared between atoms
Ionic bond
electrons are transferred from one atom to another
Molecule
atoms held together by only covalent bonds
Bond length
the distance between the nuclei of 2 atoms when they are at their lowest possible energy state
Bond dissociation energy/bond energy
the energy necessary for a complete separation of the bond
Partial ionic character
when the difference in electronegativity is significant
Dipole moment
occurs when the center of positive charge in a bond does not coincide with the center of negative charge
Intermolecular attractions
attractions between separate molecules due to dipole moments
Hydrogen bond
the strongest type of dipole-dipole interaction; occurs between a H that is covalently bound to a F, O, or N and a F, O, or N from another molecule
Induced dipole
occurs when dipole moment is momentarily induced in an otherwise nonpolar molecule or bond by a polar molecule, ion, or electric field
Instantaneous dipole moment
arise spontaneously and occur because the electrons move about and at any given moment they may not be distributed exactly between the 2 bonding atoms even when the atoms have equivalent electronegativity
London dispersion forces/Van der Waals forces
weakest dipole-dipole force between 2 instantaneous dipoles
Empirical formula
the smallest ratio of whole numbers that can be used to represent these proportions
Molecular formula
represents the exact number of elemental atoms in each molecule
Physical reaction
when a compound undergoes a reaction and maintains its molecular structure ie. melting, evaporation, dissolution, and rotation of polarized light
Chemical reaction
when a compound undergoes a reaction and changes its bonding or structure to form a new compound ie. combustion, metathesis, and redox
Combination Reaction
A + B –> C
Decomposition reaction
C –> A + B
Single Displacement/Replacement
A + BC –> B + AC
Double Displacement/Replacement or Metathesis
AB + CD –> AD + BC; often occurs between ionized salts dissolved in water
runs to completion
means that the reaction generates products until the supply of at least one reactant is fully depleted
Limiting reactant
the first reactant to be used up first
Theoretical yield
the amount of product that should be created when a reaction runs to completion based on the stiochiometry
Percent yield
actual yield/theoretical yield x 100%
Actual yield
the amount of product created by a real experiment
mole
6.022 x 10^23 of something; grams/mw
Avogadro’s number
6.022 x 10^23
Radioactive decay
atoms that spontaneously break apart
Half-life
the length of time necessary for one half of a given substance to decay
Type of decay of radioactive decay
exponential decay
Semi-log plot
plotting the logarithm of amount of atoms as a function of time would produce a straight line for something that exponentially decays
4 variables of a half-life
- initial amount of substance 2. final amount of substance 3. length of the half life 4. the number of half lives (often give as a time period in which you divide by the length of the half-life)
Alpha decay
the loss of an alpha particle/helium nucleus
Beta decay
the breakdown of a neutron into a proton and electron and the expulsion of the newly created electron
Neutrino
also emitted during beta decay; virtually a massless particle
Positron emission
the emission of a positron when a proton becomes a neutron; type of beta decay; neutrino also emitted
Electron capture
the capture of an electron and the merging of that electron with a proton to create a neutron
Gamma ray
a high frequency photon that has no mass or charge and does not change the identity of the atom from which it is given off
Gamma decay
often accompanies the other types of radioactive decay; can occur when an electron and positron collide
Valence
the number of bonds an atom usually forms
Formal charge
the number of valence electrons of an atom, minus the number of bonds it is a part of, minus the number of nonbonding electrons it has
Dash formula
shows the bonds between each atom of a molecule but does not show lone pairs nor the three dimensional structure of the molecule
Condensed formula
shows neither the bonds nor the 3D structure
Bond-line formula
line intersections, corners and endings represent a carbon atom unless another atom is drawn in; hydrogens are not drawn
Fischer projection
vertical lines are assumed to be oriented into the page and horizontal lines are assumed to be oriented out of the page
Newman projection
a view straight down the axis of one of the sigma bonds which gives information about steric hindrance with respect to a particular sigma bond
Dash-line wedge formula
the solid black wedges represent bonds coming out of the page and the dashed wedges represent bonds going into the page
Space-filling model
a 3D representation of a molecule with spheres of various colors representing different elements with respect to their relative sizes
Ball and sticks model
bond lengths are drawn to approximately twice their length so that the atoms are clearly visible; give information about relative size of atoms
Sigma bond
forms when the bonding pair of electrons are localized to the space directly between the two bonding atoms; lowest energy, strongest and most stable covalent bond
Pi bind
created by overlapping p orbitals; double and triple bonds are made by adding pi bonds to a sigma bond
How to determine number and type of hybrid orbital
count the number of sigma bonds and lone pairs of electrons on that atom, match this number to the sum of the superscripts in a hybrid name
Valence shell electron pair repulsion (VSEPR)
the electrons in an orbital seek to minimize their energy by moving as far away from other electron pairs as possible, minimizing the repulsive forces between them
Shape/ bond angle of sp
linear, 180
Shape/ bond angle of sp2
trigonal planar, 120
Shape/ bond angle of sp3
tetrahedral, trigonal pyramidal or bent, 109.5
Shape/ bond angle of sp3d
trigonal-bipyramidal, see-saw, t-shaped, or linear; 90, 120
Shape/ bond angle of sp3d2
octahedral, square pyramidal, or square planar, 90
Delocalized electrons
bonding electrons which are spread out over 3 or more atoms
Resonance structures
molecules containing delocalized electrons can be represented by a combination of 2 or more alternative Lewis structures called resonance structures; weighted average represents the actual molecule
Aromaticity
the increased stability of a cyclic molecule due to electron delocalization; must follow Huckel’s rule
Huckel’s rule
planar monocyclic rings whose number of pi electrons can be described with the equation 4n + 2 will be aromatic (lone pairs count as pi electrons)
Nucelophilic functional groups
have a partial negative charge and seek positively charged nuclei ; they donate electrons and attack functional groups with partial positive charges ie. amines
Electrophilic functional groups
have a partial positive charge and seek electrons; usually get attacked by electrons from other functional groups
Stereochemistry
three-dimensional structure of a molecule
Isomers
molecules that share the same molecular formula
Structural isomer
have the same molecular formula but different bond-to-bond connectivity and thus different chemical properties due to differences in functional groups
Conformational isomers/conformers
different spatial orientations of the same molecule
Stereoisomers
2 unique molecules with the same molecular formula and the same bond-to-bond connectivity
Enantiomers
non-superimposable mirror images of one another; same molecular formula and connectivity but are not the same molecule because they differ in their configuration; have the same chemical and physical characteristics except for interactions with other chiral molecules and interactions with polarized light