unit 2 Flashcards
includes all unit 2 power point information and practice problems (not including math)
periodic law original
when the elements are arranged in order of increasing atomic mass, certain sets of properties recur periodically
quantum mechanics explains
why periodic trends exist
metals preperties
solids at room temp
lustrous
good conductors
malleable
ductile
loses electrons to form cations
nonmetals properties
gases/brittle solids at room temp
poor conductors
gains electrons to form anions
metalloids
poor conductors at room temp
better conductors at high temps
alkali metals properties
oxides dissolve in water to form strong basic solutions
corrode in air to dull gray appearance
react vigorously to produce hydrogen
readily form compounds with nonmetals
s1 electron configuration
cations with 1+charge
gets larger as move down group
alkaline earth metals
not as reactive as alkali metals
readily form compounds with nonmetals
forms alkaline oxides, some have low solubility in water
s2 electron configuration
cations with +2 charge
halogens properties
most reactive nonmetals
F and Cl are gases, Br is liquid, I is solid
exist as diatomic molecules
readily forms compounds with metals and nonmetals
s2p5 electron configuration
gains electrons to have a 1- charge
shares electrons with nonmetals
noble gases
unreactive
s2p6 outer electron configuration
stable octet
low reactivity
isoelectronic
has same electron configuation
transition metals properties
closer to nucleus than representative metals
solid
high melting and boiling points
similarities in properties in a group and across a period
forms cations with multiple charges, forms complex ions
some have characteristic colors
3 factors of periodic trends
nuclear charge
number of core electrons
distance of outer electrons from the nucleus
coulomb’s law
e = 1/4piCo q1q2/r
e: potential energy
q1q2: charges
r: separation
coulomb’s law
strength of interaction increases as charge increases
attractive force between electron and nucleus depends on magnitude of nuclear charge (atomic number) and average distance between nucleus and electron (energy levels)
shielding
repulsions cause electron to have net reduced attraction to nucleus
effective nuclear charge
amount of attraction electron feels for nucleus
2 types of shielding
shielding by core electrons (efficient)
shielding from outer electrons (not efficient)
Zeff =
Z (actual charge of nucleus) - S (charge screened by other electrons)
atomic radius
1/2 distance between 2 atoms
bond lengths calculation
add atomic radii or 2 bonding atoms
cations are _ than their neutral atoms
smaller
anions are _ than their original atom
larger
ionization energy
minimum energy needed to remove an electron
greater IE = harder to remove an electron
increases are electrons are removed, significant jump when an entire energy level is removed
first ionixation energy
energy needed to remove the first electron
lowest
electron affinity
energy change when atom gains electron
greater attraction between atom + added electron = more negative EA
positive EA = electron won’t attach itself
halogens have most negative
electronegativity
ability of an atom in a molecule to attract shared electrons to itself
higher EN = pulls bonded electron closer
smaller atoms = higher EN
spectroscopy
studies transmission/reflection of different frequencies of electromagnetic spectrum by a sample of matter
photoelectron spectroscopy
core more difficult to remove than valence
uses higher energy light: UV to X-rays
UV studies valence
X-rays studies core
how to do photoelectron spectroscopy
- beam of x-rays shone on sample (e=hv)
- atoms of sample release electrons from any energy level (photoelectric effect)
- kinetic energy measured (binding energy = hv - KE)
PES spectrum
graph of binding energy (x-axis) and relative number of electrons (y-axis)
height of each peak is proportional to # of electrons of equal energy
UV and visible light spectroscopy
white visible light shone on colorful molecules + transition metal ions
doesn’t remove electrons from atom
excites electrons to higher energy state
electrons absorb certain wavelengths and transmit other wavelengths, producing color
reference blank
when other compounds in a solution absorbs the same wavelengths as compound being analyzed
beer’s law
A = Ebc
A=absorbance
E=molar absorbance
b=path length
c=concentration
calibration curves
direct relationship between absorbance and concentration
prepare solutions of known concentrations and analyze at ymax
plot absorbance as function of concentration
used to find the concentration of an unknown solution
meter
m
length
kilogram
kg
mass
second
s
time
Pascal
Pa
pressure
kelvin
K
temp
liter
L
volume
mole
mol
amount of substance
SI system
dominant system of measurement
giga
1,000,000,000
mega
1,000,000
kilo
1,000