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The Parts of the Atom
e-
1-
Electron cloud
around the nucleus
1/1,840
p
1+
nucleus
1
n
0
nucleus
1
Which two particles are responsible for the mass of an atom?
Which two particles are responsible for the charge of an atom?
Protons and Neutrons
Protons and Electrons
26
Fe
Iron
55.845
Atomic Number =
Atomic Mass =
Mass # =
# of Protons =
# of Neutrons =
# of Electrons =
Atomic NumberAtomic Number
Atomic MassAtomic Mass
2626
55.84555.845
5656
2626
2626
3030
Different Elements—Different Numbers of Protons
The type of
element
the number of protons
the number of electrons
What are the atomic numbers of carbon, nitrogen and oxygen? Carbon = 6, Nitrogen = 7, Oxygen = 8
Explain the difference between an oxygen atom and a carbon atom.
Oxygen has 8 protons. Carbon has 6 protons.
Neutrons and Isotopes
• Isotopes are atoms of the same element that have different numbers of neutrons. Most elements have several isotopes.
Same Different
How do the carbon isotopes differ? Carbon isotopes have different numbers of neutrons
Atomic Number vs. Mass Number
The number of
protons
The number of
protons and neutrons
Hint :
# of neutrons = mass # - protons
The average atomic mass of an element is the average mass of the element’s isotopes, weighted according to the abundance of each isotope.
Average Atomic Mass
The abundance of each isotope is changed to decimal form. The mass of each isotope is multiplied by it’s corresponding decimal percentage. All the values are added together to determine the average atomic mass
0.989 x 12 = 11.8680.0101 x 13= + 0.143 12.011
How is the average atomic mass calculated?
