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PCAT: General Chemistry
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PCAT: General Chemistry PCAT: General Chemistry PCAT: General Chemistry
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PCAT: General Chemistryisotopes - ANS an element that differs in mass numbers and neutrons but has the same number of
protons (atomic number)
Quantum theory - ANS developed by Max Planck proposing that E emitted as electromagnetic radiation
from matter comes in discrete bundles called quanta. E of a quantum from equation E=hf (h=Planck's
constant f=frequency of radiation)
Bohr Model - ANS electron can exist only in certain fixed-energy states. E of an electron is quantized.
smaller the radius, the lower the E state of the electron. this model is used to explain atomic emission
spectrum and atomic absorption spectrum of Hydrogen
Heisenberg uncertainty principle - ANS it is impossible to simultaneously determine the momentum and
position of an electron
four quanta numbers - ANS n=size
l=shape
ml=orientation of the orbital
ms= spin
principal quantum number (n) - ANS represents the shell where an electron is present in an atom.
corresponds with that element's period in the periodic table. diff in E between adjacent shells decreases
as the distance from the nucleus inc
azimuthal (angular momentum) quantum number (l) - ANS tells the shape of orbitals and subshells.
subshells include 0,1,2,3 corresponds to s,p,d,f subshells. the max number of electrons that can exist
within a subshell is 4l+2. greater value of l, the greater the E of the subshell
,magnetic quantum number (ml) - ANS describes orientation of the orbital in space. specifies the
particular orbital within a subshell where an electron is highly likely to be found at a given point in time
s subshell: 0
p subshell: -1,0,1
d subshell: -2,-1,0,1,2
f subshell: -3,-2,-1,0,1,2,3
spin quantum number (ms) - ANS 2 spin orientations are +(1/2) and -(1/2)
whenever 2 electrons are in the same orbital they must have opposite spins
bronsted lowry acid and base - ANS acid- species that donates protons
base- species that accepts protons
lewis acid and base - ANS acid- electron pair acceptor
base- electron pair donor
conjugate acid - ANS forms when a base gains a proton
conjugate base - ANS forms when an acid loses a proton
the weaker the acid, the _____ the ka (acid dissociation constant) - ANS smaller
the weaker the base, the ______ the kb (base dissociation constant) - ANS smaller
T/F: the larger the ka (the stronger the acid), the smaller the conjugate's kb (weaker the base) - ANS true
, valence electrons - ANS electrons in the outermost shell. involved in chemical bonding and determine
the chem reactivity and properties of the element
atomic radius - ANS - equal to one half the distance between the centers of the 2 atoms of that element
that are just barely touching each other
- electron cloud occupies majority of volume
- left to right of period, atomic radius decreases. greater the positive charge experienced by valence e-
the closer e- are pulled toward nucleus
- top to bottom of group atomic radius increases. valence e- within group the same but it is found
farther from the nucleus bc they're in larger energy shells so they feel less pull from nucleus
- cations smaller than neutral atoms (fewer e-)
- anions larger than neutral atoms (more e-)
what affects atomic radius? - ANS something that affects the size of the electron could will change the
radius of an atom but altering size of nucleus will not directly affect the size of the atom
ionization energy - ANS - E required to remove an e- completely from a gaseous atom or ion
- requires input of E, endothermic
- closer and more tightly bound an e- is to nucleus, more difficult it will be to remove and the higher the
ionization E
- left to right of period= inc
- top to bottom group=dec
- second ionization E is always greater than 1st ionization E
electron affinity - ANS - E change that occurs when e- is added to gaseous atom and represents ease
when an atom can accept an e-
- left to right of period= inc
- top to bottom group=dec
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