21 Atom
Warm - Up: proton, neutron
Today:
1. Check Density HW
2. Notes: Atoms
3. Study Guides
September 23
Reminders:
Six Weeks Test Thursday

36. proton positively charged subatomic particle found in nucleus of an atom
Draw it: Connect it: found in nucleus heavy, 1 amu
2

37 . neutron
Draw it: neutral subatomic particle found in nucleus of an atom
Connect it: no charge heavy, 1 amu
3

HELIUM ATOM
Shell proton
+
N
N
+
-
electron neutron
Notice the location of each particle!!!

Let’s Explore some Models of Atoms...
Activity
:
Observe the “petri dish” model of an atom.
Draw what you see and write at least three observations.
Complete the chart & Questions.

+
+
+
6

Notes: Parts of an Atom
There are two main regions within an atom:
-the
is located in the center of the atom and contains the protons and the neutrons
(it is the denser part because it has the larger massive particles)
-the
cloud that surrounds the nucleus and contains electrons, makes up most of the volume of atom, it is 100, 000 times bigger than nucleus)

Atoms are made up of three main subatomic particles :
PROTONS have a positive (+) charge and are located in the nucleus.
NEUTRONS have no charge and are located in the nucleus.
ELECTRONS have a negative (-) charge and are located outside the nucleus.

In any NEUTRAL atom , three things are equal---- atomic number, number of electrons, & number of protons
To remember this, think of the word APE :
Atomic # All three are equal. If
Protons you know one, you
Electrons know the other two.

Determining the Identity of an
Element
Each element on the Periodic Table is made of only one kind of atom. The number of protons determines an element’s IDENTITY
. The number of protons is represented by the
ATOMIC NUMBER
. If you interpret the the information on the Periodic Table, you can find the number of subatomic particles in an atom of a given element.

Atomic number 6
C
Carbon
12.011
element name element symbol atomic mass

To find the neutrons in the nucleus remember MAN :
Mass number - Atomic # = Neutrons

ATOMIC STRUCTURE
Draw this chart on the back of your notes.
Particle Charge Mass proton + charge 1 neutron electron
No charge
- charge
1
0

What makes a Hydrogen atom different from a Helium atom?
Hydrogen helium

ATOMIC STRUCTURE
Did you notice that…
Electrons are arranged in Energy Levels or Shells around the nucleus of an atom.
8
18
32
P + n
2
8

HELIUM ATOM
Shell proton
+
N
N
+
-
electron neutron
Notice the location of each particle!!!

He
ATOMIC STRUCTURE
Atomic number the number of protons in an atom
Atomic mass the number of protons and neutrons in an atom
ALL atoms are NEUTRAL!!!! Therefore,
# of electrons = # of protons

ATOMIC STRUCTURE RULES!!!
•
• The
Atomic Number
= # of protons in the nucleus.
The
Atomic Mass
= # of Protons + Neutrons
• The number of Protons
=
Number of Electrons.
• Electrons orbit the nucleus in energy levels or electron shells
.
• Each shell can only carry a set number of electrons.
2, 8, 8, 18, 32

Electrons
NUCLEUS
Protons
Neutrons

P = __ e = __
N = __
HYDROGEN

P = __ e = __
N = __
HELIUM

P = __ e = __
N = __
LITHIUM

P = __ e = __
N = __
BERYLLIUM

P = __ e = __
N = __
BORON

P = __ e = __
N = __
CARBON

P = __ e = __
N = __
NITROGEN

CHLORINE
___ e -
___ P +
___ n
P = __ e = __
N = __
Complete the Chlorine atom on your own.

Fe
2
O
3
1.There are ___ elements in the formula.
2. There are ___ atoms in the formula.

32