Download How do Atoms differ?

Honors ch 4.3
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An English scientist
Discovered each element contains a unique
positive charge in the nucleus
The number of protons in the nucleus of an
atom identifies the element – atomic number
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Because all atoms are neutral, the number of
protons and electrons in an atom must be
equal
Atomic number = # protons = # electrons
Element Atomic #
Pb
82
Protons Electrons
8
30
Element Atomic #
Pb
82
Protons Electrons
82
82
8
30
Element Atomic #
Pb
82
O
8
Protons Electrons
82
82
8
8
30
Element Atomic #
Pb
82
O
8
Zn
30
Protons Electrons
82
82
8
8
30
30
How many protons and electrons are in:
a. radon
b. magnesium
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An atom of an element contains 66
electrons. What element is it?
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An atom of an element contains 14
protons. What element is it?
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Dalton was incorrect about atoms being
indivisible and stating that all atoms of an
element are identical. (#2 and #5)
All atoms of a particular element have the
same number of protons and electrons but
the number of neutrons in the nucleus can
differ.
Isotopes – atoms with the same number of
protons but different numbers of neutrons
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All Isotopes of a specific element have
the same chemical behavior
(determined by electrons)
Isotopes are identified with a mass
number
Mass number = atomic # + # neutrons
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In nature most elements are found as
a mixture of isotopes
Ex: copper – two types found naturally
- 29 protons and 34 neutrons
- 29 protons and 36 neutrons
Cu – 63; Copper – 63,
63Cu, 63
29Cu
Cu – 65; Copper – 65,
65Cu, 65
29Cu
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Atoms are measured in amu (atomic
mass units). (based on carbon -12)
1 amu is almost equal to 1 proton or
neutron
Atomic mass – the weighted average
mass of the isotopes of that element.
Because isotopes have different masses,
the weighted average mass is NOT a
whole number.
Element
Atomic #
Mass #
Neon
Calcium
Oxygen
Iron
Zinc
Mercury
10
20
8
26
30
80
22
46
17
57
64
204
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Calculate the atomic mass of unknown
Element X. Identify the unknown element.
Isotope
Mass (amu)
Percent
Abundance
6X
6.015
7.59%
7X
7.016
92.41%
Boron has two naturally occurring isotopes:
boron-10 (abundance =19.8%; mass = 10.013
amu) and boron-11 (abundance = 80.2% and
mass = 11.009 amu) . Calculate the atomic
mass of boron.