1.13.2: Elements, Atoms, and the Periodic Table (Exercises)

These are homework exercises to accompany Chapter 2 of the Ball et al. "The Basics of GOB Chemistry" Textmap.

 The Elements

Exercises

1. Which of the following substances are elements?

   1. sodium
   2. milk
   3. gold
   4. water
   5. air
   6. liquefied nitrogen

2. Which of the following substances are elements?

   1. paper
   2. electricity
   3. neon
   4. carbon
   5. wood
   6. concrete

3. Write the chemical symbol for each element.

   1. silver
   2. sulfur
   3. nitrogen
   4. neon

4. Write the chemical symbol for each element.

   1. bromine
   2. oxygen
   3. lithium
   4. boron

5. Explain why it is improper to write CO as the chemical symbol for cobalt.

6. Explain why it is improper to write NO as the chemical symbol for nobelium.

7. Complete the following table.

   Element Symbol	Element Name
   F
   Fe
   I
   Cr
   C
   P

8. Complete the following table.

   Element Symbol	Element Name
   Mg
   Mn
   Ca
   Cl
   K
   Pt

Answers

1.  

   1. element
   2. not an element
   3. element
   4. not an element
   5. not an element
   6. element

2.

1. not an element
2. not an element
3. element
4. element
5. not an element
6. not an element

3.  

   1. Ag
   2. S
   3. N
   4. Ne

4.

1. Br
2. O
3. Li
4. B

5. By convention, the second letter in an element’s symbol is always lowercase.

6. By convention, the second letter in an element’s symbol is always lowercase. Additionally, NO represents a compound.

 

7.

Element Symbol	Element Name
F	fluorine
Fe	iron
I	iodine
Cr	chromium
C	carbon
P	phosphorus

8.

Element Symbol	Element Name
Mg	magnesium
Mn	manganese
Ca	calcium
Cl	chlorine
K	potassium
Pt	platinum

Atomic Theory

Exercises

1. Which of the following elements exist as diatomic molecules?

   1. helium
   2. hydrogen
   3. iodine
   4. gold

2. Which of the following elements exist as diatomic molecules?

   1. chlorine
   2. potassium
   3. silver
   4. oxygen

3. Why is it proper to represent the elemental form of helium as He but improper to represent the elemental form of hydrogen as H?

4. Why is it proper to represent the elemental form of chlorine as Cl₂ but improper to represent the elemental form of calcium as Ca₂?

Answers

1.  

   1. no
   2. yes
   3. yes
   4. no

2.

1. yes
2. no
3. no
4. yes

3. Hydrogen exists as a diatomic molecule in its elemental form; helium does not exist as a diatomic molecule.

4. Chlorine exists as a diatomic molecule in its elemental form; calcium does not exist as a diatomic molecule.

 

The Structure of Atoms

Exercises

1. Which is smaller—an electron or a helium atom?

2. Which is larger—a proton or an atom of lead?

3. Which subatomic particle has a positive charge? Which subatomic particle has a negative charge?

4. Which subatomic particle is electrically neutral? Does it exist inside or outside the nucleus?

5. Protons are among the (most, least) massive subatomic particles, and they are found (inside, outside) the nucleus.

6. Electrons are among the (most, least) massive subatomic particles, and they are found (inside, outside) the nucleus.

7. Describe why Rutherford used the term planetary model to describe his model of atomic structure.

8. Why is the planetary model not an appropriate way to describe the structure of an atom?

9. What happened to most of the alpha particles in Rutherford’s experiment? Explain why that happened.

10. Electrons account for the (majority, minority) of the (mass, volume) of an atom.

Answers

1. An electron is smaller.

2. An atom of lead is larger.

3. proton; electron

4. neutron; inside the nucleus

5. most; inside

6. least; outside

7. Electrons are in orbit about the nucleus.

8. Electrons do not have specific circular orbits about the nucleus.

9. Most of the alpha particles went through the metal sheet because atoms are mostly empty space.

10. minority; mass

 

Nuclei of Atoms

Exercises

1. How many protons are in the nucleus of each element?

   1. radon
   2. tungsten
   3. chromium
   4. beryllium

2. How many protons are in the nucleus of each element?

   1. sulfur
   2. uranium
   3. calcium
   4. lithium

3. What are the atomic numbers of the elements in Exercise 1?

4. What are the atomic numbers of the elements in Exercise 2?

5. How many electrons are in neutral atoms of the elements in Exercise 1?

6. How many electrons are in neutral atoms of the elements in Exercise 2?

7. Complete the following table.

   Number of Protons	Number of Neutrons	Element Name	Isotope Symbol
   80	120
   			\(\mathrm{^{55}_{26}Fe}\)
   	2	hydrogen

8. Complete the following table.

   Number of Protons	Number of Neutrons	Element Name	Isotope Symbol
   			\(\mathrm{^{3}_{2}He}\)
   95	153
   	21	potassium

9. State the number of protons, neutrons, and electrons in neutral atoms of each isotope.

   1. ¹³¹I
   2. ⁴⁰K
   3. ²⁰¹Hg
   4. ¹⁹F

10. State the number of protons, neutrons, and electrons in neutral atoms of each isotope.

    1. ³H
    2. ¹³³Cs
    3. ⁵⁶Fe
    4. ²⁰⁷Pb

11. What is the mass number of a gallium atom that has 38 neutrons in it?

12. What is the mass number of a uranium atom that has 143 neutrons in it?

13. Complete each sentence.

    1. ⁴⁸Ti has _____ neutrons.
    2. ⁴⁰Ar has _____ neutrons.
    3. ³H has _____ neutrons.

14. Complete each sentence.

    1. ¹⁸O has _____ neutrons.
    2. ⁶⁰Ni has _____ neutrons.
    3. ¹²⁷I has _____ neutrons.

Answers

1.  

   1. 86
   2. 74
   3. 24
   4. 4

2.

1. 16
2. 92
3. 20
4. 3

3. 86, 74, 24, and 4

4. 16, 92, 20, 3

5. 86, 74, 24, and 4

6. 16, 92, 20, 3

7. Number of Protons	Number of Neutrons	Element Name	Isotope Symbol
   80	120	mercury	\(\mathrm{^{200}_{80}Hg}\)
   26	29	iron	\(\mathrm{^{55}_{26}Fe}\)
   1	2	hydrogen	\(\mathrm{^{3}_{1}H}\)

8.

Number of Protons	Number of Neutrons	Element Name	Isotope Symbol
2	1	helium	\(\mathrm{^{3}_{2}He}\)
95	153	americium	\(\mathrm{^{248}_{95}Am}\)
19	21	potassium	\(\mathrm{^{40}_{19}K}\)

 

9.  

   1. protons: 53; neutrons: 78; electrons: 53
   2. protons: 19; neutrons: 21; electrons: 19
   3. protons: 80; neutrons: 121; electrons: 80
   4. protons: 9; neutrons: 10; electrons: 9

10.

1. protons: 1; neutrons: 2; electrons: 1
2. protons: 55; neutrons: 78; electrons: 55
3. protons: 26; neutrons: 30; electrons: 26
4. protons: 82; neutrons: 125; electrons: 82

11. 69

12. 235

13.

1. 26
2. 22
3. 2

14.

1. 10
2. 32
3. 74

 Atomic Masses

Exercises

1. What is the atomic mass of zinc in atomic mass units?

2. What is the atomic mass of barium in atomic mass units?

3. What is the average mass of a single magnesium atom in grams?

4. What is the average mass of a single calcium atom in grams?

5. What is the mass of 1.000 × 10²⁴ aluminum atoms in grams?

6. What is the mass of 5.000 × 10²³ carbon atoms in grams?

7. Which has more mass—1 tungsten atom or 11 oxygen atoms?

8. Which has more mass—1 magnesium atom or 6 helium atoms?

9. Determine the atomic mass of lithium, given the isotopic composition: 92.4% lithium-7 (mass 7.016 u) and 7.60% lithium-6 (mass 6.015 u).

10. Determine the atomic mass of neon, given the isotopic composition: 90.48% neon-20 (mass 19.992 u), 0.27% neon-21 (mass 20.994 u), and 9.25% neon-22 (mass 21.991 u).

11. Determine the atomic mass of magnesium, given the isotopic composition: 78.70% magnesium-24 (mass 23.98 u), 10.13% magnesium-25 (mass 24.99 u) and 11.17% magnesium-26 (mass 25.98).

12. Determine the atomic mass of bromine, given the isotopic composition: 50.69% bromine-79 (mass 78.9183 u), 49.31% and bromine-81 (mass 80.9163 u). 

Answers

1. 65.4 u

2. 137.33 u

3. 4.038 × 10⁻²³ g

4. 6.657 × 10⁻²³ g

5. 44.81 g

6. 9.974 g

7. 1 tungsten atom

8. 1 magnesium atom

9. 6.94 u

10. 20.18 u

11.  24.30 u

12.  79.90 u

The Periodic Table

Exercises

1. Which elements have chemical properties similar to those of magnesium?

   1. sodium
   2. fluorine
   3. calcium
   4. barium
   5. selenium

2. Which elements have chemical properties similar to those of lithium?

   1. sodium
   2. calcium
   3. beryllium
   4. barium
   5. potassium

3. Which elements have chemical properties similar to those of chlorine?

   1. sodium
   2. fluorine
   3. calcium
   4. iodine
   5. sulfur

4. Which elements have chemical properties similar to those of carbon?

   1. silicon
   2. oxygen
   3. germanium
   4. barium
   5. argon

5. Which elements are alkali metals?

   1. sodium
   2. magnesium
   3. aluminum
   4. potassium
   5. calcium

6. Which elements are alkaline earth metals?

   1. sodium
   2. magnesium
   3. aluminum
   4. potassium
   5. calcium

7. Which elements are halogens?

   1. oxygen
   2. fluorine
   3. chlorine
   4. sulfur
   5. carbon

8. Which elements are noble gases?

   1. helium
   2. hydrogen
   3. oxygen
   4. neon
   5. chlorine

9. Which pairs of elements are located in the same period?

   1. H and Li
   2. H and He
   3. Na and S
   4. Na and Rb

10. Which pairs of elements are located in the same period?

    1. V and Nb
    2. K and Br
    3. Na and P
    4. Li and Mg

11. In each pair of atoms, which atom has the greater atomic radius?

    1. H and Li
    2. N and P
    3. Cl and Ar
    4. Al and Cl

12. In each pair of atoms, which atom has the greater atomic radius?

    1. H and He
    2. N and F
    3. Cl and Br
    4. Al and B

13. Scandium is a (metal, nonmetal, semimetal) and is a member of the (main group elements, transition metals).

14. Silicon is a (metal, nonmetal, semimetal) and is a member of the (main group elements, transition metals).

Answers

1.  

   1. no
   2. no
   3. yes
   4. yes
   5. no

2.

1. yes
2. no
3. no
4. no
5. yes

3.  

   1. no
   2. yes
   3. no
   4. yes
   5. no

4.

1. yes
2. no
3. yes
4. no
5. no

5.  

   1. yes
   2. no
   3. no
   4. yes
   5. no

6.

1. no
2. yes
3. no
4. no
5. yes

7.  

   1. no
   2. yes
   3. yes
   4. no
   5. no

8.

1. yes
2. no
3. no
4. yes
5. no

9.  

   1. no
   2. yes
   3. yes
   4. no

10.

1. no
2. yes
3. yes
4. no

11.

1. Li
2. P
3. Cl
4. Al

12.

1. H
2. N
3. Br
4. Al

13. metal; transition metals

14. semimetal; main group elements

 

" Elements, Atoms, and the Periodic Table" by LibreTexts is licensed under CC BY-NC-SA .