General Chemistry Flashcards
Mass Number (A)
sum of the protons and neutrons in the atom’s nucleus
Atoms that share an atomic number but have different mass numbers.
Isotopes
different number of neutrons
Atomic Number (Z)
number of protons found in that element
The electrons closer to the nucleus have [higher or lower] energy levels compared to those further out?
close = LOW energy
far = HIGH energy
Atomic Mass/Mass Number vs Atomic Weight
Atomic Mass/Mass Number is the cold sum of the number of protons and neutrons
Atomic Weight the the WEIGHTED AVERAGE of all the different isotopes that exist of an atom
A mole is equal to …
Avogadro’s Number
Na = 6.02 x 10^23
What is the equation for the Planck relation?
E = hf
An electron can be excited and jump into a higher orbit. When it returns to its ground state, it releases a discrete amount of energy in the form of a photon. The equation to describe the electromagnetic energy of these photons is …
E = hc / gamma
h = Planck’s constant
c = speed of light ina vacuum
gamma = wavelength of the radiation
Pauli Exclusion Principle
no two electrons in a given atom can possess the same set of four quantum numbers
Principle Quantum Number
denoted by the letter n
the energy level and radius of the electron shell
Azimuthal Quantum Number
angular momentum designated by the letter l
shape and number of subshells within a given principle energy level (n // shell)
l = 0 to (n-1)
l = 0 is the s shell
l = 1 is the p shell
l = 2 is the d shell
l = 3 is the f shell
Maximum number of electrons within a subshell related to the Azimuthal Quantum Number
max number of electrons = 4l + 2
Magnetic Quantum Number
designated my m_l
specifies the particular orbital within a subshell where an electron is likely to be found
each orbital can hold a max of TWO electrons
m_l ranges from -l to +l, including 0
Spin Quantum Number
denoted by m_s
opposite spin (-0.5 and +0.5) when in the same orbital
Aufbau Principle
electrons fill from lower- to higher-energy subshells
each subshell will fill completely before electrons move to the next one
Hund’s Rule
within a given subshell, orbitals are filled such that there a maximum number of half-filled orbitals with parallel spin
Why would Chromium’s electron configuration be [Ar] 4s1 3d5 INSTEAD of [Ar] 4s2 3d4
half-filled and fully filled orbitals have LOWER ENERGIES (higher stability)
Hund’s Rule
Paramagnetic
material composed of atoms with UNPAIRED electrons
aligns to the magnetic field and is slightly attracted
parallel spins
Diamagnetic
materials consisting of atoms with PAIRED electrons
slightly repelled by a magnetic field
What is the maximum number of the electrons allowed in a single atomic energy level in terms of the principle quantum number n?
2n^2
Which equation describes the maximum number of electrons that can fill an orbital in terms of the Azimuthal quantum number l?
4l + 2
What is the MCAT’s favorite equation?
E = hf = h * c / lambda (wavelength)
Sublimation
phase change during which a SOLID turns into a GAS
Deposition
phase change during which a GAS turns into a SOLID
What influences the physical properties of a solid?
The LATTICE structure
includes its density and packing (influences density and melting point)
What does the roman numeral in the Group name on the periodic table represent?
i.e Group VA
the number of valence electrons elements in that group have in their neutral state
Effective Nuclear Charge (Zeff)
what is the general trend on the periodic table?
electrostatic attraction between the valence shell electrons and the nucleus
measure of he net positive charge experienced by the outermost electrons
same period: Zeff increases from left to right; more or less constant among elements in a given group
What is the trend of atomic radii on the periodic table?
SMALLER up and to the right
right – increasing Zeff of adding protons holds the valence electrons tighter/closer
up – decreasing the principle quantum number n results in shells that are closer to the nucleus
Ionization Energy (IE)
periodic trend?
energy required to remove an electron from a gaseous species
NOTE: removing electron always requires the input of energy, which makes it an ENDOTHERMIC process
the greater the atoms Zeff, the harder it is to strip the electron; IE increases then from left to right and bottom to top
Which atoms have the highest ionization energies? Which have the highest second ionization energies?
Noble Gases have the highest ionization energies
Group IA molecules have disproportionately high second ionization energies because losing one electron makes them very stable!
Electron Affinity
refers to the energy dissipated by a gaseous species when it gains an electron
EXOTHERMIC process that expels heat
HALOGENS are greedy for electrons
functionally, this is the opposite concept as ionization energy
What is the deltaH of an atom gaining an electron?
deltaH < 0 negative
EXOTHERMIC; lets off energy/heat
the HIGHER/STRONGER the Zeff, then the more energy will be released
Electronegativity
measure of the attractive force that an atom will exert on an electron in a chemical bond
related to ionization energy
Alkali Metals
Group I metals
usually exist as univalent cations that form bonds with nonmetals
Alkaline Earth Metals
Group II
usually in the form of a divalent cation
“active” metal
Double replacement reaction?
Two compounds turn into TWO NEW compounds (ion swap).
