The Atom
1. Evolution of the Atom: (Include any relevant experiments)
A. John Dalton’s model of the atom – the atom is a small, dense particle; matter is made of
atoms; atoms are indivisible
B. JJ Thomson’s model of the atom – “plum pudding”; discovered the electron using the
cathode ray tube; negative charges scattered throughout
C. Ernest Rutherford’s model of the atom – gold foil experiment; atoms have a positively
charged center
D. Bohr’s model of the atom – electrons circle the nucleus in fixed circular paths
E. Quantum model of the atom – electrons exist in orbitals; can only guess where an electron is
with a 90% accuracy
2. Define each term:
A. Atomic number: # of protons; whole # on the periodic table
B. Mass number:# of protons + # of neutrons; NOT the number on the periodic table
C. Average atomic mass: mass according to the periodic table; weighted average of all isotopes
for that element
D. Ion: an atom that has a charge; results because there is an unequal # of protons and
electrons
E. Isotope: atoms of the same element with different #’s of neutrons; results in different mass
numbers
3. Atoms are made of ____protons_______, _____neutrons______, and _____electrons_____.
A. Protons have a mass of __1___ amu and a charge of __+1____.
B. Neutrons have a mass of __1___ amu and a charge of __0____.
C. Electrons have a mass of ___0__ amu and a charge of __-1____.
4. Complete the following table:
Name
Symbol
Atomic #
Mass #
# of
protons
# of
neutrons
# of
electrons
Copper-64
Calcium-41
Strontium88
Lithium-8
Chlorine-35
Magnesium25
64 Cu
29
41Ca
29
20
38
64
41
88
29
20
38
35
21
50
29
20
38
3
17
12
8
35
25
3
17
12
5
18
13
3
17
10
88 Sr
38
8
3Li
35Cl-1
25 Mg+2
12
5. Show the equation for each of the following:
A. U-238
B. Rn – 222
undergoes alpha decay
238
92U
undergoes beta decay
238
undergoes alpha decay
222
undergoes beta decay
92U
86Rn
222
86Rn
4
2He
+
234
90Th
-1
β +
4
2He
-1
β +
238
+
93Np
218
84Po
222
87Fr
6. Calculate the average atomic mass for Ne given the following isotopes and their abundance.
Neon-20=90.92%
20.18amu
Neon-21=0.257%
Neon-22=8.82%