Download Chapter 2 Atoms and Elements

Chapter 3
Atoms and Elements
The Atom
Atomic Number and Mass Number
Ions & Isotopes
1
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 together
to form compounds
2
History of the atom
• Not the history of atom, but the idea of the
atom
• Original idea Ancient Greece (400 B.C..)
• Democritus Greek philosopher
3
Another Greek
•
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•
•
•
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Aristotle - Famous philosopher
All substances are made of 4 elements
Fire - Hot
Air - light
Earth - cool, heavy
Water - wet
Blend these in different proportions to get
all substances
Hyle
4
. e-
nucleus
5
Who’s Next?
• Late 1700’s - John Dalton- England
• Teacher- summarized results of his
experiments and those of other’s
• In Dalton’s Atomic Theory
• Combined ideas of elements with that of
atoms
6
Dalton’s Atomic Theory
 All matter is made of tiny indivisible
particles called atoms.
 Atoms of the same element are identical,
those of different atoms are different.
 Atoms of different elements combine in
whole number ratios to form compounds
 Chemical reactions involve the
rearrangement of atoms. No new atoms
are created or destroyed.
7
Location of Subatomic Particles
10-13 cm
electrons
protons
nucleus
neutrons
10-8 cm
•
8
Subatomic particles
Actual
Name Symbol Charge mass (g)
Relative
mass
Electron
e-
-1
Proton
p+
+1 1.67 x 10-24
1
Neutron
n0
0
1.67 x 10-24
1
9.11 x 10-28 1/1840
9
Subatomic particles
Relative
Name Symbol Charge mass
Relative
Mass (amu)
Electron
e-
-1
1/1840
0
Proton
p+
+1
1
1
Neutron
n0
0
1
1
10
Subatomic Particles
Particle
Symbol
Charge
Relative
Mass
0
Electron
e-
1-
Proton
p+
+
1
Neutron
n
0
1
11
Atomic Number
Counts the number
of
protons
in an atom
12
Atomic Number on the Periodic
Table
Atomic Number
Symbol
11
Na
13
All atoms of an element have the
same number of protons
11 protons
Sodium
11
Na
14
Learning Check
State the number of protons for atoms of
each of the following:
A. Nitrogen
B. Sulfur
C. Barium
15
Solution
State the number of protons for atoms of each of the
following:
A. Nitrogen
7 protons
B. Sulfur
16 protons
C. Barium
56 protons
16
Number of Electrons
 An atom is neutral
 The net charge is zero
 Number of protons = Number of electrons
 Atomic number = Number of electrons
17
All atoms of an element have the same
number of protons and electrons
11 protons
Sodium
11
11 electrons
Na
18
Atomic Mass
Atomic mass is the weighted average mass
of all the atomic masses of the isotopes of
that atom.
19
Atomic Mass on the Periodic Table
Atomic Number
Symbol
Atomic Mass
11
Na
22.989770
20
Atomic Mass on the Periodic Table
Atomic Number
11
Symbol
Na
Atomic Mass
22.989770
Mass #
23
21
Mass Number
Determined by : the whole Number closest
to the atomic mass
Counts the number of protons and neutrons
in an atom
22
Atomic Symbols
 Show the mass number and atomic number
 Give the symbol of the element
mass number
23
Na
11
sodium-23
atomic number
23
Subatomic Particles in Some
Atoms
16
8O
8 p+
8n
8 e-
31
15 P
65
30 Zn
15 p+
16 n
15 e-
30 p+
35 n
30 e24
Isotopes
 Atoms with the same number of protons, but
different numbers of neutrons.
 Atoms of the same element (same atomic
number) with different mass numbers
Isotopes of chlorine
35Cl
37Cl
17
17
chlorine - 35
chlorine - 37
25
Naturally occurring hydrogen consists of three
isotopes, protium (H-1),deuterium (H-2), and
tritium (H-3). State the number of protons, neutrons,
and electrons in each of these atoms.
1H
1
2H
1
3H
1
#p _______
_______
_______
#n _______
_______
_______
#e _______
_______
_______
26
Naturally occurring hydrogen consists of three
isotopes,
protium
deuterium
tritium
1H
1
2H
1
3H
1
#p
1
1
1
#e
1
1
1
#n
0
1
2
27
An atom of zinc - ( Zn-65)
A. Number of protons in the zinc atom
B. Number of neutrons in the zinc atom
C. What is the mass number of a zinc isotope
with 37 neutrons?
28
An atom of zinc - ( Zn-65)
A. Number of protons in the zinc atom
1) 30
B. Number of neutrons in the zinc atom
2) 35
C. What is the mass number of a zinc isotope
with 37 neutrons?
3) 67
29
Write the atomic symbols for atoms with the
following:
A. 8 p+, 8 n, 8 e-
___________
B. 17p+, 20n, 17e-
___________
C. 47p+, 60 n, 47 e-
___________
30
Solution
16O
A. 8 p+, 8 n, 8 e-
B. 17p+, 20n, 17e-
8
37Cl
17
C. 47p+, 60 n, 47 e-
107Ag
47
31
IONS
 Atoms with a charge
(positive or negative)
 Atoms which gain or lose an electron
#p
#e
#p
#e
atom
11
11
atom
17
17
ion
11
10
ion
17
18
Na
Cl
1+
1-
32
IONS
#p
#e
#p
#e
atom
12
12
atom
8
8
ion
12
10
ion
8
10
Mg
O
2+
2-
33
Complete Atomic Symbol
combines isotopes and ions
Mass #
27
Atomic #
13
13p+
Al
10e-
3+
Ionic charge
14n
34
Learning Check
14
7N
7p+
7n
10e-
3-
32 315 P
65
2+
30 Zn
15 p+
17 n
18 e-
30 p+
35 n
28 e35
Example of an Average Atomic
Mass
Cl-35 is about 75.5 % and Cl-37 about
24.5% of natural chlorine.
35 x 75.5 = 26.4
100
35.5
37 x 24.5 =
9.07
100
36