Name ___________________________________________________
Date _____________________
Period ___________________________________
Introduction to the Modern Concept of Atomic Structure
1. The nucleus of an atom contains __________________, which are positively charged.
2. Compared to the diameter of the atomic nucleus, the average distance of the electrons form the
nucleus is relatively (small/large).
3. The nucleus of an atom may also contain _________________, which are uncharged.
4. The proton and the (electron/neutron) have almost equal masses. The proton and the
(electron/neutron) have charges that are equal in magnitude but opposite in nature.
5. Although the nucleus of an atom is very important, it is the __________ of the atom that
determine its chemical properties.
Isotopes
1. True or false. Atoms that have the same number of neutrons but different numbers of protons
are called isotopes.
2. True or false. The mass number of a nucleus represents the number of protons in the nucleus.
3. For an atom, the number of protons and electrons is (different/ the same).
4. The ____________ number represents the sum of the number of protons and neutrons in a
nucleus.
5. Are all atoms of the same element identical? If not, how can they differ?
______________________________________________________________________________
______________________________________________________________________________
6. For each of the following atomic numbers, write the name and chemical symbol of the
corresponding element.
a. 46 _____________________________________________________________________
b. 78_____________________________________________________________________
c. 15_____________________________________________________________________
d. 94_____________________________________________________________________
e. 5______________________________________________________________________
f. 4_______________________________________________________________________
g. 56______________________________________________________________________
h. 83______________________________________________________________________
i. 38______________________________________________________________________
j. 19______________________________________________________________________
k. 3_______________________________________________________________________
l. 48______________________________________________________________________
m. 13______________________________________________________________________
n. 27______________________________________________________________________
o. 53______________________________________________________________________
7. Write the atomic symbol (ᴬzX) for each of the isotopes described below.
a. Z = 8, number of neutrons = 9 ______________________________________
b. The isotope of chlorine in which A = 37 ______________________________
c. Z = 27, A = 60 ___________________________________________________
d. Number of protons = 26, number of neutrons = 31 _____________________
e. The isotope of I with a mass number of 131 ___________________________
f. Z = 3, number of neutrons = 4 ______________________________________
g. Z = 13, number of neutrons = 14 ____________________________________
h. Z = 13, A = 27 ___________________________________________________
i. The isotope of aluminum with 14 neutrons in its nucleus ________________
j. The isotope with 16 protons and 16 neutrons _________________________
k. The isotope of sulfur with mass number 32 ___________________________
l. Z = 16, A = 32 ___________________________________________________
8. How many protons and neutrons are contained in the nucleus of each of the following atoms?
In an uncharged atom of each element, how many electrons are present?
Protons
Neutrons
Electrons
a. ₁₂²⁴Mg _________________________________________________________
b. ³⁴₁₆S___________________________________________________________
c. ⁴⁵₂₁Sc___________________________________________________________
d. ⁵²₂₄Cr___________________________________________________________
e. ⁵³₂₄Cr___________________________________________________________
f. ⁵⁴₂₄Cr___________________________________________________________
g. ⁶⁰₂₇Co __________________________________________________________
h. ³³₁₆S____________________________________________________________
i. ⁱ⁰₄Be____________________________________________________________
j. ⁴⁰₁₈Ar___________________________________________________________
k. ²³₁₁Na___________________________________________________________
l. ⁸⁴₃₆Kr___________________________________________________________
9. Complete the following table.
Name
Symbol
Atomic Number
Mass Number
Neutrons
Sodium
11
23
Nitrogen
ⁱ⁵₇N
ⁱ³⁶₆Ba
Lithium
6
Boron
5
11
Chlorine
18
Neon
10
Helium
2
Sodium
12
Calcium
21