ATOMIC STRUCTURE
NAME DANIEL DIZON
Atoms are composed of three sub-atomic particles: the proton, the neutron, and the electron. The proton
and the neutron are found in the nucleus. Electrons are found in a cloud surrounding the nucleus.
The atomic number of an element is equal to the number of protons in that element. If the atom is neutral,
the number of electrons is equal to the number of protons.
If the atom carries a charge, it is referred to as an ion. The charge on an ion indicates an imbalance
between protons and electrons. If the ion has a positive charge, there are more protons than electrons. To
find the number of electrons, you must subtract the charge from the atomic number. If the ion has a
negative charge, there are more electrons than protons. To find the number of electrons, you must add the
charge to the atomic number.
The mass number is a whole number equal to the number of protons plus neutrons. This number is not on
the periodic table. The atomic mass is the weighted average atomic mass of all the naturally occurring
isotopes of an element. This number is located on the periodic table and is usually a decimal.
(Remember, an isotope is an atom of the same element with a different number of neutrons; an ion is an
atom of the same element with a different number of electrons.)
Mass number
Charge
Atomic number
Element symbol
Complete the chart.
Atomic
Number
Element/Ion
1H
1
1H1+
1
14N37
41Ca
20
108Ag
47
108Ag1+
47
Mass
Number
Atomic Mass
Protons
Neutrons
Electrons
1
1.00784
1
1
1
1
1
1.00784
1
1
1
0
7
14.007
14
7
7
10
20
40.078
41
20
21
20
47
107.868
108
47
61
47
47
107.868
108
47
61
46
Define the following:
Atomic Number The number of protons in an atom.
Mass Number The number of protons and neutrons in an atom.
Isotope Name
Argon-40
Isotope
Symbol
40
Ar
Protons
Number of…
Neutrons
Electrons
Atomic
Number
Mass
Number
18
22
18
18
40
18
20
18
18
38
83
126
83
83
209
18
38
Ar
Argon-38
18
Bismuth-209
209
Bi
83
Iron-57
57
26
Fe
26
27
26
26
57
Lead-209
209
82
Pb
82
127
82
82
209
16
18
16
16
34
28
30
28
28
58
28
34
28
28
62
37
48
37
37
85
13
14
13
13
27
25
30
25
25
55
20
20
20
20
40
34
S
Sulfur-34
16
58
Se
Selenium-58
28
62
Se
Selenium-62
28
85
Rb
Rubidium-85
37
27
Al
Aluminum-27
13
55
Mn
Manganese-55
25
40
Ca
Calcium-40
20
23
Se
Sodium-23
11
11
12
11
Atomic Mass The average weighted atomic mass of all isotopes of an element.
Isotope An atom of the same element with a different number of neutrons.
11
23