Name: ____________________________________
Class: _____________
Date: _____________
Lesson Assessment: Structure of the Atom
1. When the mass of the proton is compared to the mass of the electron, which of the following statements is
true?
a) The mass of the proton is about 1836 times the mass of the electron.
b) The mass of the proton is about
1 the mass of the electron.
1836
c) The mass of the proton is almost the same as the mass of the electron.
d) The mass of the proton is equal to the mass of the electron.
2. An isotope of the element carbon (C) has a mass number of 12 and 6 neutrons in its nucleus. How many
protons does this isotope of carbon have?
a) 6
b) 12
c) 12.0111
d) 18
3. Which scientist made improvements to the classical model of the atom by incorporating quantum theory?
a) Paul Dirac
b) Niels Bohr
c) Democritus
d) Ernest Rutherford
4. The element lithium (Li) has an atomic number of 3. How many protons does the element lithium have?
a) 3
b) 6.941
c) 1
d) 6
5. How many protons does 1.00 gram of protons contain?
18
a) 6.25 10
–19
b) 1.60 10
27
c) 1.10 10
23
d) 5.99 10
PAGE 1
Name: ____________________________________
Class: _____________
Date: _____________
Lesson Assessment: Structure of the Atom
6. The isotope tritium has 2 neutrons and an atomic number of 1. What is the mass number for tritium?
a) 3
b) 1.00794
c) 0
d) 1
7. How many electrons are needed to make a charge of 7 coulombs?
–31
a) 9.1094 10
18
b) 6.25 10
–19
c) 1.60 10
19
d) 4.375 10
8. Suppose that element Y has an atomic number of 21 and two isotopes called isotope 1 and isotope 2.
Isotope 1 of element Y has 12 neutrons and isotope 2 of element Y has 16 neutrons. Suppose that in a
natural sample of element Y about 15% of the atoms are of isotope 1 and about 85% of the atoms are of
isotope 2. What is the atomic mass of element Y?
a) 36.4
b) 29
c) 35.5
d) 21
9. Which scientist discovered the electron?
a) Ernest Rutherford
b) Democritus
c) Erwin Schrödinger
d) Joseph Thompson
10. The atomic number for the element sodium (Na) is 11. An isotope of sodium has a mass number of 23.
How many neutrons are present in this isotope of sodium?
a) 22.98971
b) 23
c) 11
d) 12
PAGE 2
ANSWER KEY
1. a
2. a
3. b
4. a
5. d
6. a
ANSWER KEY Page 1
7. d
8. a
9. d
10. d