Download Mass Number Try this: Nuclear Symbols Modern Atomic Theory

10/16/2014
Try this:
Mass Number
Mass # = p+ + n0
• Mass number = the total number of protons and neutrons (total number of particles in the nucleus)
• Mass numbers can vary among atoms of a single element, because atoms of the same element can have different numbers of neutrons
different numbers of neutrons.
• Different elements can have the same mass numbers, because the mass number does not help you identify the element, the atomic number does! Nuclear Symbols
•
•
235U 92
235 is the mass number of Uranium
92 is the atomic number of Uranium
• A uranium nucleus has 92 protons.
• It also has a total of 235 neutrons and protons in its It also has a total of 235 neutrons and protons in its
nucleus (mass number).
• How many neutrons in an atom of Uranium‐235?
• Mass # – Atomic # = # of Neutrons
• 235 (protons + neutrons) – 92 protons =
143 neutrons
Mass # = p+ + n0
Element
p+
n0
e- Mass #
Oxygen
33
Phosphorus
FIND THE NUMBER OF NEUTRONS:
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Sodium
Calcium
Nitrogen
Iron
Argon
Lithium
What does this tell you?
12
6 C
Modern Atomic Theory
• Atoms of a particular element do share the same atomic number (number of protons) and identical chemical properties but the atoms of a given element may differ in their mass numbers (number of protons and neutrons)
of protons and neutrons).
• Elements occur in nature as mixtures of isotopes.
Isotopes
• Isotopes = atoms of the same element with different numbers of neutrons and mass numbers
♦ Nuclear symbol:
Mass #
Atomic #
12
6
C
♦ Hyphen notation: carbon-12
1
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Isotopes
Isotopes
• Isotopes = atoms of the same element with different numbers of neutrons and mass numbers
♦ Nuclear symbol:
14
6
Mass #
Atomic #
C
♦ Hyphen notation: carbon-14
© Addison‐Wesley Publishing Company, Inc.
Try to determine information about these isotopes:
• Chlorine‐37
– atomic #:
17
– mass #:
37
– # of protons:
17
– # of electrons:
17
– # of neutrons:
20
37
17
Cl
• How many protons, neutrons, and electrons make up an atom of Br‐80?
Protons + Neutrons = 80
Protons = 35
Electrons = 35
Neutrons = 80 – 35 = 45
• How many protons, neutrons, and electrons make up an atom of C‐14?
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Protons + Neutrons = 14
Protons = 6
Electrons = 6
Neutrons = 14 – 6 = 8
Isotope
Protons Electrons Neutrons Nucleus
Hydrogen–1
(protium)
Hydrogen-2
(deuterium)
Using Mass Numbers
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Isotopes of Hydrogen
Hydrogen-3
(tritium)
Ions
Are created when an atom loses or gains one
or more electrons; it acquires a charge
http://web.visionlearning.com/custom/chemistry/animations/CHE1.3-an-ions.shtml
Charge of Ion = number of protons – number of electrons
More electrons than protons = negative charge (anion)
More protons than electrons = positive charge (cation)
12
6
C +1
# of protons →
# of electrons →
Total charge →
2
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PRACTICE IONS
Ion
# protons
# neutrons # electrons
Li +1
Ni +2
Pb +2
Ca +2
Cs +1
3