midterm Flashcards
5 traditional areas of chemistry
organic
inorganic
biochem
analytical (quantitative and qualitative)
physical
crystalline solid
long-range, repeating order
amorphous solid
no order
decanting
gradually pouring a liquid from one container to another without disturbing the sediment
distillation
mixture is heated to boil off the more volatile (easily vaporable) liquid, then the liquid is re-condensed in a condenser and collected in a separate flask
filtration
used to separate a mixture of an insoluble solid and liquid
physical property
property that a substance displays without changing its composition
ex. taste, color, melting point, density
chemical property
property that substance displays only by changing its composition via a chemical change
-often indicated by temperature, color change, gas production
ex. flammability, corrosiveness, flammability
physical change
alters physical state/appearance of matter (no change in composition)
ex. water boiling
chemical change
alters the composition of matter
ex. iron rusting
Kelvin calculations:
K = C + 273
C = K - 273
Fahrenheit calculations:
F = 1.8 (C) + 32
C = (F - 32) / 1.8
error =
experimental value - accepter value
percent error =
|error|/accepted value x100
error| / accepted value x 100%
density =
mass/volume
volume =
mass/density
length x width x height
mass =
density x volume
density _ as temperature _
decreases, increases
democritus contributed:
atoms were indivisible and indestructible
democritus limited:
didn’t explain chemical behavior
lacked experimental support
dalton contributed:
all elements are composed of atoms
atoms of the same element are identical
atoms of one element are different than atoms of another element
Law of Definite Proportions
chemical reactions occur when atoms are separated, joined, or rearranged
atoms of one element are never changed into atoms of another element in a chemical reaction
Law of Definite Proportions
atoms of different elements can physically mix together/combine in simple whole-number ratios to form compound
thomson contributed:
cathode ray tube experiment
electrons
plum pudding model
cathode ray tube experiment
electric currents passed through gases in a cathode ray tube
cathode ray traveled from the cathode to the anode
cathode ray deflected by a magnet
cathode ray deflected by charged plates
plum pudding model
showed an atom has electrons evenly dispersed throughout
rutherford contributed:
gold foil experiment
the atom is mostly empty space and all the positive charge and almost all of the mass comes from the nucleus
gold foil experiment
directed a narrow beam of alpha particles at a very thin sheet of gold foil
alpha particles scattered from the gold foil
rutherford was limited:
didn’t explain chemical properties of elements
why negatively charged electrons were not pulled into the positively-charged nucleus
why atoms don’t glow
law of conservation of mass
in a chemical reaction, matter is neither created nor destroyed
law of definite proportions
all samples of a given compound have the same proportions of their constituent elements
law of multiple proportions
when two elements (A and B) form two different compounds, the masses of element B that combine with element A can be expressed as a ratio of small whole numbers
of neutrons =
mass # - atomic #
avg. atomic mass =
calculate mass contributions
add products
mass contributions =
isotope mass x natural abundance
atomic mass unit
1/12 the mass of a Carbon-12 atom
Mendeleev
arranged elements by increasing atomic mass
Moseley
determined atomic numbers for known elements
periods
rows
groups
columns
periodic law
elements arranged by increasing atomic number
electromagnetic radiation
light acting as a wave
amplitude determines
lights intensity/brightness
electromagnetic spectrum:
radio waves
microwaves
infrared
visible light
UV light
x-ray
gamma
constructive interference
interaction between 2 in-phase waves to make one large wave
destructive interference
interaction between 2 out-of-phase waves to make a line
diffraction
when traveling waves encounter an obstacle or opening in a barrier that is about the same size as the wavelength, they bend around it
interference pattern
diffraction of light through 2 slits separated by a distance comparable to the wavelength
destructive interference: dark areas
constructive interference: light areas
photoelectric effect
many metals emit electrons when light shines on its surface
energy that exceeds that threshold frequency becomes kinetic energy
atomic spectroscopy
wave nature of particles
emission spectrum
emitted light is passed through a prism
pattern of wavelengths of light is seen
flame test of mercury
blue
flame test of helium
violet
flame test of hydrogen
red
quantized states
electron should only give off specific amounts of energy
stationary states
electrons travel in orbits that are at a fixed distance from the nucleus
bohr’s model limitations:
only explained hydrogen’s emission spectrum
didn’t explain why electrons don’t fall into the nucleus
bohr’s model contributions:
electrons exist only in certain energy levels
energy is involved in the transition of an electron from one energy level to another
de broglie’s contributions:
electrons exhibit wave-like properties
electrons have wavelengths
electrons have wave-particle duality
heisenberg’s contributions:
an electron’s position is an atom is not precisely defined
Heisenberg’s Uncertainty Principle
Heisenberg’s Uncertainty Principle
impossible to determine the location and speed of an electron
quantum mechanical model
precisely defines the energy of the electron
described its location in terms of probabilities
orbital
region of space around a nucleus where there is a high probability of finding an electron
n:
energy level
l:
sublevel
m:
orbital
s:
spin
Aufbau principle
electron enter low-energy orbitals first
orbitals on the same sublevel have the same energy
s sublevel has the lowest energy
Pauli Exclusion principle
an orbital can contain up to 2 electrons
electrons spin up/down
electrons behave like magnets
electrons in the same orbital have opposite spins
Hund’s rule
one electron enters each orbital
when all orbitals have one electron, they begin to pair up
quantum mechanics
explains why periodic trends in properties exist
coulomb’s law
describes attraction and repulsion between charged particles
shielding
repulsions cause the electron to have a net reduced attraction to the nucleus
Zeff =
atomic # - core electrons
atomic radius =
1/2 the distance between 2 bonded atoms
down a group, radius:
energy levels increases
increases
energy levels increases
shielding increases
nuclear charge increases
across a period, radius:
energy levels constant
decreases
energy levels constant
shielding constant
nuclear charge increases
nuclear attraction
attraction between negative electrons in their orbitals and the positive protons in the nucleus
ionization energy
energy required to remove the an electron from an atom
electronegativity
the ability of an atom of an element to attract electrons
across a period, ionization energy/electronegativity
increases
distance from nucleus constant
shielding constant
nuclear charge increases
down a group, ionization energy/electronegativity
decreases
distance from nucleus increases
shielding increases
nuclear charge increases
cation
positive ion
anion
negative ion
