-
matter is made up of particles called ___
atoms
-
who suggested the universe was made of indivisible units?
Greek philosopher Democritus
-
"atom" means?
unable to be cut or divided
-
Dalton's atomic theory
all atoms of a given element were exactly alike, and atoms of different elements could join to form compounds
-
law of definite proportions
a chemical compound always contains the same elements in exactly the same proportions by weight or mass
-
whose theory is considered the foundation for modern atomic theory?
Dalton's theory
-
for any given water sample, the proportions of hydrogen and oxygen by mass are ___
constant
-
who conducted an experiment that suggested atoms were not indivisible?
J.J. Thomson
-
mysterious rays in vacuum tubes
cathode rays
-
according to Thomson's experiment, cathode rays are made of ___ particles that came from ___
- 1. negatively charged
- 2. inside atoms
-
cathode has what type charge?
negative
-
anode has what type charge?
positive
-
negatively charged particles inside the atom
electrons
-
what did Rutherford propose?
most of the mass of the atom was concentrated at the atom's center
-
positively charged, dense core of the atom
nucleus
-
nucleus contains particles called ___ and ___
protons and neutrons
-
protons have ___ charge
positive
-
neutrons have ___ charge
no
-
the 3 main subatomic particles are distinguished by?
- mass
- charge
- location in the atom
-
tiny, negatively charged particles moving around outside the nucleus
electrons
-
the mass of an electron is ___ than that of a proton or neutron
much smaller
-
how many protons does a hydrogen atom have?
one
-
how many protons does a helium atom have?
two
-
how many protons does lithium have?
three
-
if an atom gains or loses electrons, it becomes ___
charged
-
-
force attracting positive and negative charges
electric force
-
number of protons in the nucleus of an atom
atomic number
-
sum of the numbers of protons and neutrons in the nucleus of an atom
mass number
-
an atom that has the same number of protons as other atoms of the same element, but has a different number of neutrons
isotope
-
unstable isotopes
radioisotopes
-
what does the number 235 represent in U-235?
mass number
-
unit of mass that describes the mass of an atom or molecule - equal to 1/12 the mass of a carbon-12
unified atomic mass unit (amu)
-
weighted average of an element
average atomic mass
-
collection of a very large number of particles
mole
-
mass in grams of one mole of substance
molar mass
-
who suggested that the energy of each electron was related to the electron's path around the nucleus?
Niels Bohr
-
according to Bohr's new atomic model, how do electrons behave?
like waves
-
can the exact location of an electron be determined?
no
-
region in an atom where there is high probability of finding electrons
orbital
-
what does the number of energy levels that are filled in an atom depend on?
number of electrons
-
electrons in the outer energy level of an atom
valence electrons
-
valence electrons determine what type of properties of an atom?
chemical
-
-
which orbital is the simplest?
s
-
orbital shaped like a sphere
s
-
orbital shaped like a dumbbell
p
-
how many possible p orbitals are there?
3
-
how many possible d orbitals are there?
5
-
how many possible f orbitals are there?
7
-
when do electrons jump between energy levels?
when an atom gains or loses energy
-
lowest state of energy of an electron
ground state
-
when does an electron move to an excited state?
when it gains energy
-
a unit or quantum of light
photon
-
energy of a photon is related to what?
wavelength of the light
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