1. 6 LOOKING BACK KEY CONCEPTS SUMMARY
CHAPTER 6
KEY CONCEPTS SUMMARY
Elements cannot be broken down into simpler substances.
Elements are the building blocks of all substances.
All substances on Earth are made of one or more elements.
Elements are arranged on the periodic table.
A compound is a pure substance composed of two or more different elements that are chemically joined.
LOOKING BACK

2. 6 LOOKING BACK KEY CONCEPTS SUMMARY
CHAPTER 6
KEY CONCEPTS SUMMARY
Metals and non-metals have characteristic physical properties.
Metals are elements that have lustre, and are conductors, malleable, and ductile.
Non-metals are elements that are mostly gases or dull, powdery solids.
LOOKING BACK

3. 6 LOOKING BACK KEY CONCEPTS SUMMARY
CHAPTER 6
KEY CONCEPTS SUMMARY
Elements are organized according to their atomic number and electron arrangement on the periodic table.
The columns of the periodic table represent groups or families of elements with similar properties.
Elements in the same family have the same number of electrons in their outermost orbits.
LOOKING BACK

4. 6 LOOKING BACK KEY CONCEPTS SUMMARY
CHAPTER 6
KEY CONCEPTS SUMMARY
Atomic models evolved as a result of experimental evidence.
John Dalton proposed that matter is made of tiny indivisible particles called atoms.
J. J. Thomson proposed that atoms are positively charged, with negatively charged electrons evenly distributed within them.
Ernest Rutherford proposed that atoms are mostly empty space, with a positively charged centre that is surrounded by negatively charged electrons.
Niels Bohr proposed that electrons occupy fixed orbits around the nucleus.
LOOKING BACK

5. 6 LOOKING BACK KEY CONCEPTS SUMMARY
CHAPTER 6
KEY CONCEPTS SUMMARY
Atoms contain protons and neutrons in a central core surrounded by electrons.
The Bohr–Rutherford model of the atom consists of positively charged protons and neutral neutrons in the nucleus and negatively charged electrons orbiting the nucleus.
LOOKING BACK

6. 6 LOOKING BACK KEY CONCEPTS SUMMARY
CHAPTER 6
KEY CONCEPTS SUMMARY
Elements can be both beneficial and harmful to humans and to the environment.
Some elements are harmful to humans in very small quantities.
Some elements are essential nutrients that humans and other living things need in order to survive.
Some elements are beneficial to humans, but their extraction can be harmful to the environment.
LOOKING BACK

7. QUIZ
CHAPTER 6
MULTIPLE CHOICE
For each question, select the best answer from the four alternatives.
1. Which of the following correctly describes the mass number of an element?
(a) the number of protons in the atom’s nucleus
(b) the number of electrons in the atom’s electron orbits
(c) the number of neutrons in the atom’s nucleus
(d) the number of protons and neutrons in the atom’s nucleus
2. What do we call a horizontal row in the periodic table?
(a) a chemical family
(b) a period
(c) an isotope
(d) an element

8. QUIZ
CHAPTER 6
MULTIPLE CHOICE
For each question, select the best answer from the four alternatives.
3. From the information in the periodic table, how many neutrons does the most common isotope of oxygen have?
(a) 6
(b) 7
(c) 8
(d) 10
4. The current version of the periodic table of elements originates from a table that was developed by
(a) J. J. Thomson
(b) Niels Bohr
(c) Dmitri Mendeleev
(d) Ernest Rutherford

9. QUIZ
CHAPTER 6
FILL IN THE BLANKS
Fill in the blanks with a that correctly completes the sentence.
5. An atom of Na-22 will have ___________ protons in its nucleus, ___________ neutrons in its nucleus, and ______________ electrons in its electron orbits.
6. Columns of elements in the periodic table are known as ___________________.

10. QUIZ
CHAPTER 6
MATCHING
Match each contribution on the left with the name of the scientist who made the contribution on the right. 7.

11. QUIZ
CHAPTER 6
SHORT ANSWER
8. How many protons, neutrons, and electrons are there in an atom of Cl-35?
9. Draw Bohr–Rutherford diagrams for the first three elements in the alkaline earth metal family.
10. Describe and explain any identifiable patterns that emerge from the series of Bohr–Rutherford diagrams in question 9.

12. 6 QUIZ ANSWERS MULTIPLE CHOICE
CHAPTER 6
MULTIPLE CHOICE
1. Which of the following correctly describes the mass number of an element?
(a) the number of protons in the atom’s nucleus
(b) the number of electrons in the atom’s electron orbits
(c) the number of neutrons in the atom’s nucleus
(d) the number of protons and neutrons in the atom’s nucleus
2. What do we call a horizontal row in the periodic table?
(a) a chemical family
(b) a period
(c) an isotope
(d) an element

13. 6 QUIZ ANSWERS MULTIPLE CHOICE
CHAPTER 6
MULTIPLE CHOICE
3. From the information in the periodic table, how many neutrons does the most common isotope of oxygen have?
(a) 6
(b) 7
(c) 8
(d) 10
4. The current version of the periodic table of elements originates from a table that was developed by
(a) J. J. Thomson
(b) Niels Bohr
(c) Dmitri Mendeleev
(d) Ernest Rutherford

14. 6 QUIZ ANSWERS FILL IN THE BLANKS
CHAPTER 6
FILL IN THE BLANKS
5. An atom of Na-22 will have 11 protons in its nucleus, 11 neutrons in its nucleus, and 11 electrons in its electron orbits.
6. Columns of elements in the periodic table are known as chemical families (or groups).
MATCHING 7.
(a) (iv), (b) (v), (c) (ii), (d) (i), (e) (iii)

15. 6 QUIZ ANSWERS SHORT ANSWER
CHAPTER 6
SHORT ANSWER
8. How many protons, neutrons, and electrons are there in an atom of Cl-35?
There are 17 protons, 18 neutrons and 17 electrons.
9. Draw Bohr–Rutherford diagrams for the most common isotopes of the first three elements in the alkaline earth metal family.
10. Describe and explain any identifiable patterns that emerge from the series of Bohr–Rutherford diagrams in question 9.
These three elements all have two electrons in their outermost electron orbit.