Download Atomic Number Reference Table page 9 Mass Number Try this

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Reference Table page 9
Atomic Number
• Because atoms are neutral, they must have the equal numbers of protons and electrons.
• Therefore, the atomic number tells us how many protons and also how many electrons an
many protons and also how many electrons an atom has.
How many PROTONS and ELECTRONS are in:
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Silver
Hydrogen Neon
Gold
Boron
Sodium Tungsten 47
1
10
79
5
11
74
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! Try this:
Nuclear Symbols
Mass # = p+ + n0
Element
p+
Oxygen
33
Phosphorus
n0
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e- Mass #
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
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Modern Atomic Theory
FIND THE NUMBER OF NEUTRONS:
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• 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.
Sodium
Calcium
Nitrogen
Iron
Argon
Lithium
What does this tell you?
12
6 C
Isotopes
Isotopes
• Isotopes = atoms of the same element with different numbers of neutrons and mass numbers
♦ Nuclear symbol:
Mass #
Atomic #
♦ Nuclear symbol:
12
6
♦ Hyphen notation: carbon-12
Isotopes
• Isotopes = atoms of the same element with different numbers of neutrons and mass numbers
14
6
Mass #
C
Atomic #
C
♦ Hyphen notation: carbon-14
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
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Isotopes of Hydrogen
Isotope
Using Mass Numbers
Protons Electrons Neutrons Nucleus
Hydrogen–1
(protium)
• How many protons, neutrons, and electrons make up an atom of Br‐80?
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Hydrogen-2
(deuterium)
Protons + Neutrons = 80
Protons = 35
Electrons = 35
Neutrons = 80 – 35 = 45
• How many protons, neutrons, and electrons make up an atom of C‐14?
Hydrogen-3
(tritium)
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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
Protons + Neutrons = 14
Protons = 6
Electrons = 6
Neutrons = 14 – 6 = 8
PRACTICE IONS
Ion
# protons
# neutrons # electrons
Li +1
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 →
Ni +2
Pb +2
Ca +2
Cs +1
3