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Gen. Chem. Chapter 1
general chemistry notecards for MCAT prep
26
Chemistry
Graduate
05/20/2011

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Cards

Term
isotopes
Definition
chare an atomic number but have different mass numbers
Term
AZ X
Definition

A = mass number of the atome

Z = atomic number

X = the atom

Term
Electrons
Definition

electrons close to the nucleus = ower electric potential energy

eleectrons closer to outer regions or shells = higher electric potential energy

 

Term
Valence electrons
Definition

electrons in the outtermost energy level or shell

 

experience the least electrostatic draw to their nucleus = more likely to become involved in bonds with other atomes

Term
Atomic mass
Definition
atomic mass = the sum of protons and neutrons
Term
Atomic weight
Definition

mass in grams of one mole of atoms

a mole = 6.02 x 1023

Term
isotopes of Hydrogen
Definition

protium: one proton and atomic mass of 1 amu

deuterium: 1 proton and 1 neutron; atomic mass of 2 amu

tritium: 1 proton and 2 neutrons; atomic mass of 3 amu

Term

quanta

 

Definition
decrete bundles of energy emitted as EM radiation that comes from matter
Term
energy value of a quantum
Definition

E = hƒ

 

where h = Planck's constant = 6.626 x 10-34 Jxs

and ƒ = frequency of radiation

Term
Angular momentum of an electron
Definition

L = nh/2π

where h = 6.626 x 10-34 J x s

and n = quantum number (which can be any positive integer)

 

note: because n is the only variable integer in the formula, the angular momentum of an electron changes only in discrete amounts with respect to the quantum number

Term
Energy of the electron
Definition

E = -RH / n2

where RH = Rydberge constant = 2.18 x 10-18 J/electron

note: according to this equation, the energy of the electron changes in discrete amounts with respect to the quantum number as well

note: the electron in any of its quantized states in the atom will have a negative energy as a result of the attractive forces between the electron and the proton

note: the energy of an electron increases the further out from the nucleus that it is located

Term
ground state of hydrogen
Definition
the orbit with the smallest radius in which hydrogen's electron could be found; corresponds to n = 1
Term
excited state of hydrogen
Definition
when the electron was promoted to a higher energy orbit (one with a larger radius)
Term
electromagnetic energy of photons
Definition

E = hc/λ

 

where h = planck's constant = 6.626 x 10-34

and c = speed of light = 3 x 108

and λ = the wavelength of the radiation

Term
Balmer series
Definition

hydrogen emission lines of transitions from levels n > 2 to energy level n = 2

inclues 4 wavelengths of visible light

Term
Lyman series
Definition

hydrogen emission lines corresponsding to transitions from the n > 1 to n =1 energy levels

 

inclues larger energy transitions = shorter photon wavelengths in the UV region of the EM spectrum

Term
Energy emitted by a photon
Definition

E = hc/λ = -RH[1/ni2 - 1/nf2]

 

the energy of the emitted photon corresponds to the precise difference in energy between the higher energy initial state and the lower energy final state

Term
Heisenberg uncertainty principle
Definition

it is impossible to simultaneously determine, with perfect accuracy, the momentum and the position of an electron

 

if we want to assess the position of an electron: the electron must stop = changing its momentum

 

if we want to assess the momentum of the electron: the electron has to be moving = changing its position

Term
Pauli Exclusion Principle
Definition
no two electrons in a given atom can possess the same set of 4 quantum numbers
Term
Principal Quantum Number (n)
Definition

can take on any positive integer value

 

the larger the integer value = the higher the energy level and radius of the electron's orbit(al)

 

within each shell of some n value, maxim number of electrons = 2n2

 

the difference in energy between 2 shells decreases as distance from the nucleus increases

Term
Azimuthal (Angular Momentum) Quantum Number (l)
Definition

refers to the shape and number of subshells within a give nprincipal energy level (shell)

 

has important implicatiosn for chemical bonding and bond angles

 

the value of n limit the value of l: range of possible l value is 0 to (n-1)

 

l = 0; s-subshell

l = 1; p-subshell

l = 2; d subshell

l = 3; f-subshell

 

max. number of electrons in a subshell: 4l + 2

Term
Magnetic Quantum Number (ml)
Definition

specifices the particular orbital within a subshell where an electron is highly likely to be found at a given moment in time

 

each orbital can hold a max. number of electron of 2

 

possible values of ml = -l to +l including 0

Term
Spin Quantum number (ms)
Definition

electron has two spin orientations designated by +1/2 and -1/2

 

2 electrons in the same orbital must have opposite spins

 

electrons in different orbitals with the same spinal = parallel spins

Term
Hund's Rule
Definition
within a given subshell, orbitals are filled such that there are a maximum number of half-filled orbitals with parallel spins
Term
Paramagnetic
Definition
materials that have magnetic fields made of atoms with unpaired electrons that cause the unpaired electrons to orient their spins in alignment with the magnetic field and the material will be weakly attracted to the magnetic field
Term
Diamagnetic
Definition
materials consisting of atoms that have all paired electrons and will be slightly repelled by a magnetic field
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