WEIGHING & COUNTING
ATOMS
Multiple Choice
1. The atomic number of
oxygen, 8, indicates that there are eight
(A) protons
in the nucleus of an oxygen atom
(B) oxygen
nuclides
(C) neutrons
outside the oxygen atom's nucleus
(D) energy
levels moving around each oxygen nucleus
2. The number that is the
total number of protons and neutrons in the nucleus of an atom is the
(A) atomic
number
(B) Avogadro number
(C) mass
number
(D) number of neutrons
3. Isotopes of a
particular element differ in
(A) the
number of neutrons in the nucleus
(B) atomic
number
(C) the
number of electrons in their outermost energy level
(D) the
total number of electrons
4. In determining atomic
mass units, the standard is a(n)
(A) C - 12
atom (B) C -
14 atom
(C) H - 1
atom
(D) O - 16 atom
5. The chemical shorthand
for atomic mass units is
(A) amu
(B) mu
(C) a (D) am
6. The average atomic mass
of an element is the weighted average of the atomic masses of the
(A)
naturally-occurring
isotopes (B)
two most abundant isotopes
(C) nonradioactive
isotopes
(D) artificial isotopes
7. The number of atoms in
one mole of carbon is
(A) 6.022 x
1022
(B) 6.022 x 1023
(C) 5.022 x
1022
(D) 5.022 x 1023
8. The number of atoms in
a mole of any substance is called
(A) the
atomic number
(B) Avogadro's number
(C) the mass
number
(D) the molar mass
9. As the atomic masses of
the elements in the Periodic Table increase, the number of atoms in one
mole of each element
(A)
decreases (B)
increases (C)
remains the same
(D) becomes
a negative number
Problems
10. Oxygen has two isotopes:
O-16 and O-18. Naturally-occurring oxygen consists of 99.759% of
oxygen 16. What is the
average atomic mass of oxygen according to these numbers?
11. How many neutrons does
Zn-66 (atomic number 30) have?
12. Ag-109 has 62
neutrons. How many electrons does the neutral atom have?
13. An atom of chlorine
has an atomic number of 17 and a mass number of 35. How many protons,
neutrons, and electrons does it
have?
14. Neon has 3 natural isotopes:
Ne-20 (90.51%), Ne-21 (0.27%), and Ne-22 (9.22%). What is neon's
average atomic mass?
15. What is the mass of
two moles of oxygen atoms if the average atomic mass of oxygen is 16 amu?