Basic Atomic Structure Worksheet ANSWERS
1
a) protons
b) neutrons
c) electrons
a) Positive
b) Neutral
c) negative
2
atomic number (or identity); charge
3
protons; electrons (in a neutral charge atom only!); same
4
average atomic weight; mass
5
mass number; nucleus
6
neutrons; protons (or atomic number); mass number
7
Lithium = Li = 3
Iron = Fe=26
Oxygen = O = 8
Krypton = Kr = 36
8
(A neutral atom by definition has NO charge! The protons and electrons are equal!)
Bromine = Br= 35
Copper = Cu = 29
Mercury = Hg = 80
Helium = He = 2
Uranium = U = 92
Boron = B = 5
Chlorine = Cl = 17
9
Iodine = I = 53
Xenon = Xe = 54
NOTE****For these, I rounded the average atomic weight to the nearest whole number to get
the mass number for the most abundant isotope. Mass number is the number of protons and
neutrons: this number is not on the Periodic Table. Atomic weight is the average of all isotopes
and this IS on the Periodic Table.
Barium = Ba = 137-56 = 81
Carbon = C= 12-6 = 6
Fluorine = F = 19-9 = 10
Europium = Eu = 152-63 = 89
Bismuth = Bi = 209-83 = 126
Hydrogen = H = 1-1 = 0
Magnesium = Mg = 24-12 = 12
Mercury = Hg = 201-80 = 121
10
a.) Iron
b.) Iodine
c.) Helium
d) Calcium
11
a) YES
b.) NO
c) YES
d) NO
e) Lead
f) Hydrogen
12
NOTE****For these, I rounded the average atomic weight to the nearest whole number to get
the mass number for the most abundant isotope. Average Atomic Weight does not equal Mass
Number. Tomorrow, I will either give you the mass number or you will have to figure it out by
adding the protons and the neutrons
Z = Atomic Number (see structure packet)
A = Mass Number (see Structure packet)
For the isotopic symbol, the mass number is always written on the top left side of the element
symbol. The atomic number is always written on the bottom left side of the element. The charge
(if there is one) is written on the top right side. (see Structure packet!)
If no charge is given, assume that atom is neutral (equal protons and electrons).
If you are still struggling to remember all the definitions, make notecards or use this acronym
that a colleague of mine (someone who taught many of you bio last year) uses.
“APE MAN”
APE is “Atomic Number = Protons = Electrons” (for neutral atoms only)
MAN is “Mass Number = Atomic Number – Neutrons”
A
B
C
D
E
F
G
H
I
J
K
L
M
NAME
sodium
chlorine
potassium
phosphorus
iron
iodine
silver
krypton
tungsten
copper
indium
gold
sulfur
Symbol
Na
Cl
K
P
Fe
I
Ag
Kr
W
Cu
In
Au
S
Z
11
17
19
15
26
53
47
36
74
29
49
79
16
A
23
35
39
31
56
127
108
84
184
64
115
197
32
protons
11
17
19
15
26
53
47
36
74
29
49
79
16
electrons
11
18
19
15
24
53
47
36
74
29
49
78
18
neutrons
12
18
20
16
30
74
61
48
110
35
66
118
16
Symbol
23
11Na
35
-1
17Cl
39
19K
31
15P
56
+2
26Fe
74
53I
108
47 Ag
84
36Kr
110
74W
64
29Cu
115
49In
197
+1
79Au
32
-2
16S