Download Atomic Mass

Atom
The basic building block of all
matter.
Greek for
átomos:
undivided
Material from:
http://www.mdusd.k12.ca.us/foothill/staff/elliott/notes/Atoms.htm
http://www.csmate.colostate.edu/cltw/cohortpages/viney_off/atom.jpg
A. Parts of an Atom
1. Nucleus: in the center of an atom
a. Protons:
•
•
p+
Positively charged particles in the nucleus
Have the mass of 1 atomic mass unit (1 amu)
b. Neutrons:
•
•
Neutrally charged particles in the nucleus (no
charge)
Also have mass of 1 amu. n
A. Parts of an Atom
(continued)

2. Electron Cloud: Outside the
nucleus


a. The place you’ll most likely find an
electron
b. Electrons:


e-
Negatively charged particles found in the
cloud
Have VERY little mass (1/2000 amu) so it’s
not included in an atom’s mass.
B. Atomic Number
1. The number of protons in an atom.
2. What makes each element unique.
3. The smaller number in an element’s square.
4. When drawing an atom diagram, we usually draw
the same number of electrons as protons.
5. What is the atomic number of each element and
how many protons & electrons are in each??
1.0079
12.011
238.03
C. Atomic Mass
1. It’s the sum of the protons and neutrons in an atom.
2. The unit is: amu (for atomic mass unit).
3. Number of neutrons = (Atomic Mass) – (Atomic Number)
4. What’s the atomic mass of each element?
5. How many neutrons are in each element??
1.0079
12.011
238.03
Open to your “Atoms” notes and copy this:
2-15-11
A Diagram of a Nitrogen Atom
- -e
Atomic Number:
7
N
Nitrogen
Equal to number of
protons in one atom,
as well as electrons
Electrons
(-e)
Element Symbol
Element Name
-- e
-e
-
14.01
-- e
Atomic Mass:
++n
+nn+n+
n+n+n
-
-e -e
-e
Comes from total mass
of protons+neutrons
(electrons add very little
mass)
1st
Electron
Shell: can
hold 2 -e
2nd Electron Shell:
can hold 8 -e
Nucleus area:
Protons (+) &
Neutrons (n)
D. Periodic Table of the Elements
1. This lists all elements, by atomic number
Summary – Important Things
to Remember
Atoms contain:

1.


2.


3.


Protons (+): They have a positive charge.
Atomic mass = 1 amu
# of Protons = Atomic Number
Neutrons (n): They have a neutral charge.
Atomic mass = 1 amu
# of Neutrons = (Atomic Mass) – (Atomic #)
Electrons (-): They have a negative charge.
Very small mass & are located in different energy
level shells
# of Electrons = Number of protons
D. Atom Bonds
1. Covalent Bonds

Electrons are shared between atoms

Example: Water molecules are made from 2 Hydrogen
atoms and 1 Oxygen Atom. Each Hydrogen atom has 1
electron. They are then shared with the Oxygen atom
because it can hold 2 more electrons in its outside 2nd
shell B. Ionic Bonds
2. Ionic Bonds

Electrons are transferred from one atom to another

Example: To make table salt (chemically called Sodium
Chloride), a Sodium atom gives/transfers its 1 electron that
is in its 3rd electron shell to a Chlorine atom. Sodium is
happy as its outside 2nd shell is full with 8 electrons.
Chlorine’s 3rd shell has 8 electrons and is also happy.
Covalent Bonds
Covalent Bonds
Atom Bonds
B. Ionic Bonds

Electrons are transferred from one atom to
another
 Example:
To make table salt (chemically called
Sodium Chloride), a Sodium atom gives/transfers
its 1 electron that is in its 3rd electron shell to a
Chlorine atom. Sodium is happy as its outside 2nd
shell is full with 8 electrons. Chlorine’s 3rd shell
has 8 electrons and is also happy.
Ionic Bonds