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Unit E – Atoms: Building Blocks of Matter
Section 1
______________= anything that has mass and volume
All ________________ are made of matter
_____________ = basic building blocks of matter
______________ observations = obtained without actually seeing or touching the object
_________________ = a mental picture which can change as new information is
collected
_____________________ (Greek) = named the smallest piece of matter an atom (more
than 2000 years ago)
From the Greek atomos meaning ___________________
He thought the atom was the ____________________ piece of matter
Other follower sharing his beliefs were called __________________
It took another 2000 years before an atomic model of matter was accepted
In the 1800’s John Dalton (English) proposed the _______________ theory
Dalton had been interested in ____________________ (study of weather)
He discovered that gases combine as if they were made of ________________ particles
These ________________ were the atoms of Democritus
Dalton’s Atomic Theory said:

All elements are made of ___________ and atoms are indivisible and
indestructible

Atoms of the same element are exactly _____________

Atoms of different elements are ______________

________________ are formed by joining 2 atoms of 2 or more elements
Dalton’s atomic theory is one of the foundations of modern _________________
But it was ______________ as more was learned about the structure of matter
In 1897, J.J. ________________ (English) thought that maybe the atom was made of
smaller particles
Thomson was studying the passage of ________________ current through a gas
The gas gave off particles that were ____________________charged
The charged particles had to come from within the atom so…. The atom was
_______________!
Thomson called the negatively charged particles __________________
Today we called them __________________
The atom as a whole is uncharged or neutral
If electrons were negatively charged then Thomson reasoned that there must also be
__________________ charged particles but he could not find them
Thomson proposed a model called the ___________ pudding model: the atom was
made of a _______________ like positively charged material throughout which
negatively charged _____________were scattered like plums in a pudding
In 1911, Ernest _______________ (British) added to the theory of atomic structure
Rutherford fired a stream of positively charged particles at a thin sheet of
____________ foil
Most of the positively charged “_____________” passed through
Rutherford concluded that the gold ___________ in the sheet were mostly
______________ space
Some “bullets” bounced away as if they had hit something
Rutherford knew that positive charges _______________ other positive charges
So, he proposed that the atom had a small dense positively charged center called the
_________________
The nucleus is _______________ compared to the atom as a whole
Rutherford reasoned that all of the atom’s positive charges were in the nucleus and the
negatively charged electrons were scattered outside the nucleus around the atom’s
_________________
Rutherford proposed that the electrons were held around the edge by the
____________________ between them and the positively charged nucleus (opposite
charges attract)
In 1913, Niels ____________ (Danish) proposed that each electron occupies a specific
energy level
Bohr thought that electrons moved in definite _______________ around the nucleus
These orbits were specific ___________________ from the nucleus
The orbits have only certain allowed energies called energy ______________
Bohr’s model works to explain simple atoms but not ________________ atoms
Today the atomic model is based on the principle of wave __________________
The wave model states that electrons have no ___________________ path
It is impossible to determine the exact __________________ of an electron
Can only ____________________ where an electron is likely to be found based on how
much energy the electron has
Sum of modern atomic model: atom has a small positively charged
__________________, surrounded by enough _______________ to make the atom
__________________
Section 2
Today about 200 ________________ particles are known to exist
Subatomic = smaller than an atom
The ____________ main subatomic particles are

____________ (positive charge)

Electron (_______________ charge)

Neutron (no charge/______________)
_________________ = center or core of atom
1000 x smaller than the entire atom
has ____________ and _____________ (net positive charge)
Protons = positively charged ______________ found in the nucleus
All protons are _______________
Atomic mass unit = a _______________ unit used to measure the small masses of
subatomic particles (amu)
The mass of a proton is _____________ amu
Neutrons = no charge/electrically neutral
All neutrons are _________________
Have more mass than _________________
A neutron is _________________ amu
________________ number = number of protons in the nucleus of an atom
The atomic number determines what the ________________ is
The atomic number _______________ the element
The atomic number of an element _________________ changes
The number of _______________ can change
_______________ = atoms of an element that have the same # of protons but different
#’s of neutrons
_______________ number = number (sum) of protons and neutrons in nucleus
To distinguish one isotope from another, the mass number is given with the element’s
name
The number of neutrons can be determined by _____________________ the atomic
number from the mass number
Elements occur in nature as a ________________ of isotopes
Average Atomic Mass = __________________ average of the mass #’s of the isotopes
of the element
The AAM is not usually a _____________ number
_______________ = negatively charged
Smaller than protons and neutrons
1/1836th the mass of a proton/neutron ….or about ______________ amu
Outside nucleus in energy levels occupying space called an electron _____________
The energy level determines where an electron is likely to be found (not an
____________ location)
The lowest energy level is _____________ to the nucleus
________________ energy levels are farther away from the nucleus
Each energy level can hold only a certain _____________ of electrons (2n2)
1st level = 2 electrons
2nd level = 8 electrons
3rd level = 18 electrons
Since an atom is ________________, the number of protons = the number of electrons
The _______________ of the elements depend on the #’s of electrons present
The electron arrangement determines the elements’ chemical properties and its
______________ ability
Bonding is determined by the _______________ (outermost) electrons
________________ = a new class of subatomic particles
Quarks make up all ______________ in the nucleus
Nuclear particles are __________________ of 3 quarks
There are a number of different _____________ of quarks
Quarks have properties called _____________ and color
There are six different flavors and ________________ different colors
Section 3
There are _______________ forces in the atom that account for subatomic particle
behavior
They are

_____________________ force = likes repel; opposites attract/electrons held in
orbit by this force

_____________ force = strongest force/opposes electromagnetic force of
repulsion between protons/only works when protons are very close
together/limited range

_______________ force = responsible for radioactive decay/neutron changes to
proton and electron (key to power of the sun)

________________ = force of attraction between all objects in nature/most easily
observed in large objects/weakest force known in nature
The role of gravity “________________” the atom is not clearly understood
Physicists have tried to develop a _______________ principle that would explain all four
forces in term of one _______________ force and all varieties of particles in terms of one
basic ___________________