Transcript What do atoms look like?

What do atoms look like?
What do we know about atoms?
*All elements are composed of atoms
*The atoms of the same element are the same
(and different from the atoms of any other
element)
*Atoms of different elements can mix together or
can chemically combine in a whole number ratio
to form compounds
* Chemical reactions occur when atoms are
joined, separated or rearranged. BUT you can’t
turn one element into another by chemical
reaction.
What are atoms made of?
• The three basic components of an
atom are the
–Proton
–Neutron
–Electron
Where are the subatomic particles
found?
• Proton
• Neutron
• electron
•
•
•
•
•
Found in the nucleus
Has a +1 charge
Mass of ~1amu
10-15 m in size
p+
•
•
•
•
•
Found in the nucleus
Electrically neutral
Mass of ~1amu
10-15 m in size
n̊
• Found outside the nucleus in the
“electron cloud”
• Has a -1 charge
• Mass of ~0
• 10-18 m in size
• e-
MASS?
1 amu or “atomic mass unit” is
1/12 the mass of carbon 12
SIZE?
•
The empty atom: If we imagine the atom’s nucleus to be the size of a bean,
the atom itself will become the size of a stadium, and the electrons will be
like tiny fleas whizzing frantically somewhere around the stands.
What makes the atoms of one
element different from the atoms of
another?
• The number of protons, neutron, and
electrons differs from one element to the
next.
• The number of
determines
the element.
• The number of protons is equal to the
on the periodic table
6
C
12.011
Carbon
Atomic Number = # of Protons
• Every Hydrogen atom has ____ protons
• Every Magnesium atom has ____ protons
• Every Arsenic atom has ____ protons
Atoms are electrically neutral so…
# of protons must = # of electrons
How many electrons in an atom of
Hydrogen?
Magnesium?
Arsenic?
The mass of an atom comes from
its protons and neutrons so…
Mass Number = # of protons + # of neutrons
Or
Mass number – atomic number = # of
neutrons
What is the difference between
mass number and atomic mass?
• Atomic Mass= weighted average of the
masses of all known isotopes of an
element.
• Mass Number = protons + neutrons for a
particular isotope of an element
***Round atomic mass to the nearest whole
number to get the mass number for the
most common isotope of that element.
How many neutrons in an atom of
Hydrogen?
Magnesium?
Arsenic?
Round the atomic mass to the nearest whole number
Why isn’t atomic mass a whole
number?
Because elements exist as
Atoms with the same
number of protons BUT a
different number of
neutrons
Atomic mass is
the weighted
average of all
the known
isotopes of an
element.
All atoms are isotopes, some are just more
common then others!!!
Isotopes are often represented
using isotopic notation:
Mass number
Ex.
14
Element symbol
Atomic number
6
C
• Many times the atomic number will be left
off (since that always remains the same)
ex. Carbon-14
or
14C
Did you know that
carbon -14 is used to
date fossils!
What about IONS?
• Ions are electrically charged atoms
Positive = cation = more protons then
electrons
Negative = anion = more electrons then
protons
Represented as K+1