This document discusses the structure of atoms including subatomic particles like protons, neutrons, and electrons. It explains key atomic concepts such as atomic number, mass number, isotopes, and the periodic table. The periodic table arranges elements by atomic number and can be used to find protons, electrons, atomic symbols, and average atomic masses. Atoms of the same element have the same number of protons.
2. Atomic Theory
Atoms are building blocks of elements
Similar atoms in each element
Different from atoms of other elements
Two or more different atoms bond in simple
ratios to form compounds
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6. Periodic Table
Represents physical and chemical
behavior of elements
Arranges elements by increasing atomic
number
Repeats similar properties in columns
known as chemical families or groups
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8. Atomic Number on the Periodic
Table
Atomic Number
Symbol
11
Na
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9. All atoms of an element have
the same number of protons
11 protons
Sodium
11
Na
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10. Learning Check AT 1
State the number of protons for atoms of each
of the following:
A. Nitrogen
1) 5 protons
2) 7 protons 3) 14 protons
B. Sulfur
1) 32 protons
2) 16 protons
C. Barium
1) 137 protons 2) 81 protons
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3) 6 protons
3) 56 protons
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11. Solution AT 1
State the number of protons for atoms of each
of the following:
A. Nitrogen
2) 7 protons
B. Sulfur
2) 16 protons
C. Barium
3) 56 protons
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12. Number of Electrons
An atom is neutral
The net charge is zero
Number of protons = Number of electrons
Atomic number = Number of electrons
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13. Mass Number
Counts the number
of
protons and neutrons
in an atom
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14. Atomic Symbols
Show the mass number and atomic number
Give the symbol of the element
mass number
23
atomic number
Na
sodium-23
11
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16. Masses of Atoms
A scale designed for atoms gives their small
atomic masses in atomic mass units (amu)
An atom of 12C was assigned an exact mass of
12.00 amu
Relative masses of all other atoms was
determined by comparing each to the mass of
12
C
An atom twice as heavy has a mass of 24.00
amu. An atom half as heavy is 6.00 amu. 16
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17. Atomic Mass
Na
22.99
Listed on the periodic table
Gives the mass of “average” atom of each
element compared to 12C
Average atom based on all the isotopes and their
abundance %
Atomic mass is not a whole number
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18. Learning Check AT6
Using the periodic table, specify the
atomic mass of each element (round to the
tenths place):
A. calcium
__________
B. aluminum
__________
C. lead
__________
D. barium
__________
E. iron
__________
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19. Solution AT6
Using the periodic table, specify the
atomic mass of each element (round to the
tenths place):
A. calcium
_40.1 amu _
B. aluminum
_27.0 amu _
C. lead
_207.2 amu_
D. barium
_137.3 amu_
E. iron
_55.8 amu__
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