Download The Atom - MorgansChemistry

Matter &
The Atom
Matter
The term matter describes all of the
physical substances around us
Matter is anything that has mass and
takes up space
The Universe is made up of matter and
energy
Matter is made up of atoms.
An atom is the smallest whole
particle of matter.
Subatomic particles are smaller
than atoms and are the tiny
particles that an atom is made of.
Early Models of the Atom
Rutherford
Mostly empty
space
Small, positive
nucleus
Contained protons
Negative electrons
scattered around
the outside
Early Models of the Atom
Bohr
Electrons move in
definite orbits
around the
nucleus
Modern Model of the Atom
The Electron Cloud
Sometimes called
the wave model
Spherical cloud of
varying density
Varying density
shows where an
electron is more or
less likely to be
Atomic Structure
Nucleus
– Protons
– Neutrons
Electrons
Atomic Structure
Electrons
Tiny, very light particles
Have a negative electrical charge (-)
Move around the outside of the nucleus
Atomic Structure
Protons
Much larger and heavier than electrons
Protons have a positive charge (+)
Located in the nucleus of the atom
Atomic Structure
Neutrons
Large and heavy like protons
Neutrons have no electrical charge
Located in the nucleus of the atom
Atomic Structure
Describing Atoms
Atomic Number (Z) = number of protons
In a neutral atom, the # of protons = the
# of electrons
Mass Number (A) = the number of
protons + the number of neutrons
Ions
An atom that carries an electrical
charge is called an ion.
If the atom loses electrons, the atom
becomes positively charged (because
the number of positively charged
protons will be more the number of
electrons).
Ions
If the atom gains electrons, the atom
becomes negatively charged (because
there are more negative charges than
positive).
Ions
The number of protons does not change
in an ion.
The number of neutrons does not
change in an ion.
So, both the atomic number and the
atomic mass remain the same.
Ions
This atom has lost an electron. Now it has
one more proton than electron.
One more proton means
one more positive
charge.
This makes the total
charge of the atom
POSITIVE.
Ions
This atom has gained an
electron. Now it has one
less proton than electron.
One less proton means
one less positive charge.
This makes the total
charge of the atom
NEGATIVE.
Isotopes
The number of protons for a given atom
never changes.
The number of neutrons can change.
Two atoms with different numbers of
neutrons are called isotopes
Isotopes have the same atomic #
Isotopes have different mass #’s
Isotopes
Average Atomic Mass
The average atomic mass is the
weighted average mass of all the
naturally occurring isotopes of that
element.
Average Atomic Mass
The average atomic mass of the element
is the sum of the mass contributions of
each isotope.
You are NOT responsible for knowing
how to calculate average atomic mass.