Mr. Sheehan’s Pd
Name:
Answers Chem Extra Chp 4 Practice
1. Summarize the FOUR parts of Dalton’s Atomic Theory.
Hints: Made of..., same...., combine...., chemical reactions.
a. All elements are made of atoms
b. Atoms of the same element are identical
c. Atoms combine in whole-number ratios to form compounds
d. In chemical reactions, atoms are combined, separated, or rearranged – but never changed into
atoms of another element
2. The atomic number shows the # of _protons____, which equals the number of _electrons.
3. Written as an equation, what does the mass number show?
Protons + Neutrons
4. Fill in the rest of the table using the information provided. Do not use a periodic table.
Atomic
symbol
Atomic
number
Protons
Neutrons
Electrons
Mass
Number
B
Na
Ga
Y
Cu
Tc
Yb
Ac
Tl
Fm
Sg
5
11
31
39
29
43
70
89
81
100
106
5
11
31
39
29
43
70
89
81
100
106
6
13
37
50
35
57
102
136
125
159
159
5
11
31
39
29
43
70
89
81
100
106
11
24
68
89
64
100
172
225
206
259
265
Mr. Sheehan’s Pd
Name:
5. Fill in the table given the element. Round the atomic mass to the nearest whole number.
Atomic
symbol
Atomic
Mass
Neutrons
Protons Electrons
number
Number
68
68
68
167
99
50
50
50
119
69
13
13
13
27
14
6. Find the average atomic mass of the problems below:
(Mass * percent abundance) + (Mass * percent abundanc) + (…
a. The relative abundance and atomic masses of copper isotopes are 69.2% for mass = 62.93 amu, and
30.8% for mass = 64.93 amu. Calculate the average atomic mass of copper.
(0.692 x 62.93) + (0.308 x 64.92) = 63.6 amu
b. Calculate the atomic mass of bromine. The two isotopes of bromine have atomic masses and
relative abundance of 78.92 amu (50.69%) and 80.92 amu (49.31%)
(0.5069 x 78.92) + (0.4931 x 80.92) = 79.90 amu
c. Neon has two isotopes. Neon with 19.992 amu is 90.00% abundant and the mass of 21.99 amu is
10.00% abundant. Calculate the average atomic mass of neon.
(0.9000 x 19.992) + (0.1000 x 21.99) = 20.19 amu
d. What is the atomic mass of silicon if 92.21% of its atoms have mass 27.977 amu, 4.70%
have mass 28.976, and 3.09% have mass 29.974 amu?
(0.9221 x 27.977) + (0.0470 x 28.976) + (0.0309 x 29.974) = 28.1 amu