The Atom
Unit 4 Chemistry
DO NOW
11/16/15
 Answer
the following questions
What do you know about the atom
(ex: what is it made of?)
How big is the atom?
How would you represent an atom
on paper? Draw an atom:
Video

https://youtu.be/yQP4UJhNn0I
The Atom

The atom is the smallest particle of an element
that retains the chemical properties of that
element.

Consist of smaller particles and their number and
arrangement of these particles within the atom
determine it’s chemical property

Consists of 2 regions
Atoms 2 regions
1) Nucleus: very small, located near the center of
an atom
2) Electrons: surrounds the nucleus
1) Large
region compared to nucleus
Electron
shells
Nucleus
Subatomic particles

3 subatomic particles
1.
Protons: positive charge
Within nucleus
2.
Neutrons: neutral charge
3.
Electrons: negative charge
Atomic Anatomy
The gas of an atom
What they look like
# e- = # p+
“Subatomic Particles”
Particle
(symbol)
Mass
Charge
Location
Proton
P+
1
+1
nucleus
Neutron
n0
1
0
nucleus
Electron
e-
0
-1
Outside,
orbiting the
nucleus
(for neutral atoms)
Chemical Symbol
8
O
Oxygen
15.999
Atomic #
Symbol
1st Letter
2nd letter
Name
Average
Atomic
Mass
# of p+ + # n0
# n0 = mass –atomic #
(round mass)
Practice finding # e-, p+ and n0
7
N
Nitrogen
14.01
15
P
Phosphorus
10.97
11
Na
Sodium
So how do we draw the atoms?
Ex: Li – Three protons (atomic number)
3
Li
P+
P+
P+
Lithium
6.941
Four neutron.
(mass – atomic number
n0
n0
p+
n0
p+
p+
n0
Three electrons,
in two electron shells
ee-
ee-
e-
p+
n0
p+
n0
____p+
____n0
Positions of electrons
Shell #
# of e-
1
2
Go in as a pair
2
8
1 in each of 4 places then
pair up
3
8 (sort of - more to come) 1 in each of 4 places then
pair up
4
8 (sort of – more to come) 1 in each of 4 places then
pair up
DO NOW
11/17/19
Draw
a Bohr model of sodium
11
Na
Sodium
22.990