Fundamentals of Chemistry Flashcards
what is the charge and mass of a proton
positive, and 1 amu
what is the charge and mass of a neutron
no charge, 1 amu
what is the mass and charge of an electron
negative, 0.0005458 amu
define ion
the number of protons does not equal the number of electrons
define isotope
same number of protons and electrons but a different number of neutrons
define pure substance
consists of atoms with the same number of protons, cannot be broken into simpler species
define compound
consist of more than one type of element and are held together by chemical bonds
define ionic compound
when a non-metal reacts with a metal and a transfer occurs. There is an electrostatic attraction between the opposite charges
properties of ionic compounds
high melting point and can conduct electricity when liquid
define molecular compound
covalent compounds where atoms share electrons, often non-metals
properties of molecular compounds
low melting and boiling points
define empirical formula
gives elements the smallest possible ratio
define skeletal formula
each carbon is represented by a line
define isomer
different molecules have the same formula but different connectivity
define chemical reaction
any process that leads to a chemical transformation of one or more substance into another
how many molecules does a mole contain
6.022x10^23
define attractive force
one that pushes things towards zero (makes them closer)
define repulsive force
pushes things away
define potential well
a dip in energy vs distance graph
define functional group
a part of a molecule which has distinctive chemical properties
IR light will only be absorbed when shone at a sample ifβ¦
- the energy of the radiation corresponds to the energy required to vibrate the molecule
- the vibration leads to the dipole moment of the molecule changing
what is the equation for electromagnetic radiation (speed of light)
wavelength x frequency
what is the equation for energy of a photon
plancks constant x frequency of a photon
define the Heisenberg Uncertainty Principle
we cannot simultaneously know the location and energy of an electron
define orbital
a region of the atom where an electron is most likely to reside
name the 4 different types of orbitals
different energies (n)
different shapes (l)
different orientations (ml)
different spins (ms)
what is n more commonly known as
the principle quantum number
what is l more commonly known as
the angular momentum quantum number (n-1)
what are orbitals with l=0 known as
s-orbitals
what are orbitals with l=1 known as
p-orbitals
what is an angular node
when the wave function changes sign, the point in the middle is 0, and this is an angular node, l
what are the values of ms
1/2 or -1/2
what did Pauli discover
no two electrons in the same atom can have exactly the same quantum numbers, they can share the same orbital provided ms is different, meaning there is a max of 2 electrons per orbital
list the orbitals from lowest to highest energy
s, p, d, f
describe metallic bonding
valence electrons are a long way from the nucleus and not held tightly, multiple atoms can overlap without nuclei repelling, does not require close overlap, electrons can delocalise across the system and carry charge
define power
the rate of change of energy
give the equation for power
E/t (energy/time)
define potential maximum
any change or movement will cause the energy to be lowered
define potential minimum
extra energy is needed to move it away from the minimum (most stable positions)
define Coulombβs Law
the force between two oppositely charged objects depends on the size of the charges and varies inversely with the square of the distance
if the overall charge is negative for Coulombβs equation, is the force attractive or repulsive
attractive
define binding energy
the energy given out by forming a bond
define crystalline solid
ordered at the microscopic scale, with the component atoms or molecules packing in regular or repeating way all the way through the solid
define cation
any ion with an overall positive charge
define amorphous solid
not ordered and molecules are packed at random
define anion
any ion with an overall negative charge
define lattice enthalpy
the energy change which occurs when one mole of solid forms from ions which start out indefinitely far apart, and since the lattice forms and makes bonds, the system ends up lower in energy and so we represent that as a negative enthalpy
define electronegativity
how much an element draws electrons towards itself
define the Octet rule
each atom tries to adopt a state with 8 electrons in its highest energy level
define the Bond-Oppenheimer approximation
electrons are small and can move quickly, whilst atomic nuclei are larger, heavier and do not move as fast, so we can regard the nuclei as static on the timeframe of electrons
define quantum confinement
the phenomenon by which the more localised a particle is, the higher energy it is
what are the limitations of the particle in a box model
atoms are not one dimensional, the electrostatic potential well for a Coulombic potential is not boxed shaped, and the atomic potential well is not infinitely deep as you are able to remove electrons from atoms
define valence bond theory
bonds form when two atoms orbitals overlap and share two electrons between themselves
how do we get in-phase combination
by adding two orbitals together
how do we get out-of-phase combination
by subtracting one orbital from the other
what does the in-phase combination show
constructive interaction
What is the difference between in-phase and out-of-phase combination
in-phase: the space occupied by the electrons in the combined orbital is larger than the space occupied by the electrons in the two separate orbitals
out-of-phase: the space occupied by the electron is less than that of the free atoms
define bonding orbital
the in-phase combination which produces an orbital lower in energy than the original orbitals
what is the equation for bond order
1/2 (number of electrons in bonding orbitals - number of electrons in anti-bonding orbitals)
isoelectric relationship
two compounds with different atoms and charges have the same number of electrons in the same type of orbital
define anti-bonding orbital
an out-of-phase combination which is higher in energy than the original orbitals
what are the rules for filling MO diagrams
fill from the lowest energy up
for orbitals of the same energy, electrons fill up first with spins parallel, then anti-parallel pairing
define orthogonality
two orbitals can occupy the same space but never form bonding or anti-bonding combinations with each other
define sigma symmetry
if you rotate around the axis of the atom then everything stays the same
define pi symmetry
if rotate around the axis and the wave function changes
define inversion symmetry
if (+x, +y, +z) and (-x, -y, -z) are equal and opposite
what is the label we give something if it has inversion symmetry
u, meaning ungerade
what label do we give something if πΉ(+π₯, +π¦, +π§) = πΉ(βπ₯, βπ¦, βπ§)
g, for gerade
define paramagnetic
compounds with unpaired electrons
define diamagentic
compounds with paired electrons
define s-p mixing
when the s and p orbitals on adjacent atoms can interact if they point towards each other
define molecular orbital theory
the true MOs of a molecule are formed by LACO (linear combination of AOs) and are determined by considering all of the AOs at once rather than only considering pair-wise interactions
define local orbital approximation
the idea that only nearby things will significantly affect the local environment
define conjunction
used to describe the situation when pi systems are βlinked togetherβ
define hybridization
the concept of mixing atomic orbitals to form new hybrid orbitals suitable for the pairing of electrons to form chemical bonds in valence bond theory
describe how to determine hybridization of an atom in a molecule
- Count the number of atoms (not bonds) connected to it
- Count the number of lone pairs attached to it
- Add these numbers together
- If itβs 4, the atom is sp3
- If itβs 3, the atom is sp2
- If itβs 2, the atom is sp
- If itβs 1, itβs probably hydrogen
define resonance stabilisation
the kind of stabilisation through delocalisation into conjugated systems
why is the kekule structure incorrect
- It predicts alternating short and long bonds, but all measurements are actually the same
- Double bonds react rapidly with Br2 as this is one of the common tests for alkenes, however benzene does not
- It predicts that 1,2-disubstituted benzene should show two isomers, but benzene only shows one
- Benzene is much more stable, thermodynamically speaking, than would be expected. It would be expected to be -406kJmol-1, but in reality it is -206kJmol-1
what relationship must be true for a compound to be aromatic
ππ. ππ π πππππ‘ππππ = 4π + 2 (Huckelβs rule)
what is the relationship for anti-aromatic compounds
they have 4n electrons
how does photoelectron spectroscopy work
by ionizing samples using high energy radiation (UV or X-rays) and measuring the kinetic energies of the ejected electrons
what does photoelectron spectrsocopy determine
the relative energies of electrons in atoms or molecules
