Download Atoms and Isotopes - NOTES

Atoms
&
Isotopes
NOTES
Reading the Periodic Table
A
E
M
Atomic Number
Element
Symbol
Average Atomic Mass
Reading Atoms & Isotopes
Atomic Number
A
Element Symbol
Mass Number
E
M
Or
Element Name – M
Atomic Number
• The number of Protons in
the nucleus of a given atom
• Remember – All atoms as a whole
want to have a Neutral electrical
charge.
Atomic # = the # of Protons
the # of electrons
Mass Number
• The sum of the number
of protons and number
of neutrons in the
nucleus of an atom.
• Example:
Carbon - 12
6p
+ 6n
12
Isotopes
• Atoms that have the same
number of Protons but
different numbers of
Neutrons.
Example:
Bromine - 79 = 35p and 44n
Bromine - 80 = 35p and 45n
Average Atomic Mass
• The average mass of all
isotopes of an element.
Example:
• In a sample of 100 Carbon atoms:
• 99 of them are Carbon-12 &
• 1 is a Carbon-14.
What’s the Average Atomic Mass?
12.02
Finding the # of Neutrons:
•Use the formula below:
# of Neutrons = Mass # - Atomic #
3
Li
6.94
Name:
Lithium
#p:
#e:
3
3
#n:
4
Unit of Measurement
(MASS):
Atomic Mass Unit (amu)
• one-twelfth the mass of a
carbon-12 atom. (6P & 6N)
• 1 amu = 1.665402 x 10-27 Kg
• 1p = 1.007280 amu
• 1n = 1.008670 amu
• 1e = 0.000549 amu
Practice Problems
50
Sn
Magnesium-24
118.71
Tin
Element: _________
Protons: _________
50
Electrons: _________
50
Neutrons: _________
69
Mg
Symbol: _________
Protons: ________
12
Electrons: ________
12
Neutrons: ________
12
More Practice Problems
24
79
Cr
52
Au
197
Element: Chromium
_________
Protons: _________
24
Electrons: _________
24
Neutrons: _________
28
Element: _________
Gold
Protons: ________
79
Electrons: ________
79
Neutrons: ________
118
More Practice Problems
17
Cl
35
Element: _________
Chlorine
Protons: _________
17
Electrons: _________
17
Neutrons: _________
18
17
Cl
37
Element: _________
Chlorine
Protons: 17
________
Electrons:17
________
Neutrons: 20
________