phys. sci ch 8

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Bellringers

Standards Assessment

Visual Concepts

Chapter 8 Chemical Bonding

Table of Contents

Section 1 Electrons and Chemical Bonding

Section 2 Ionic Bonds

Section 3 Covalent and Metallic Bonds

Section 1 Electrons and Chemical BondingChapter 8

Bellringer

Use the chemical formulas below and the periodic table, if necessary, to identify the atoms found in the following substances:

C6H12O6 – Glucose (a sugar)

C2H5OH – Ethyl alcohol

Then on the periodic table, locate each element that you identified. Write what you know about each compound. How are these compounds similar to or different from one another? How are these compounds different from the elements that they are composed of? Write your answers in your Science Journal.

What You Will Learn

• Chemical bonding is the joining of atoms to form new substances.

• Valence electrons are used to form chemical bonds.

• The number of valence electrons in an atom determines whether the atom will form bonds.

Combining Atoms Through Chemical Bonding

• Chemical bonding is the joining of atoms to form new substances.

• An interaction that holds two atoms together is called a chemical bond.

• When chemical bonds form, electrons are shared, gained, or lost.

Electron Number and Organization

• The number of electrons in an atom is the same as the atomic number of the element.

• Electrons in an atom are organized in energy levels.

• Most atoms form bonds using only the electrons in the outermost energy levels.

Electron Number and Organization, continued

• A valence electron is an electron that is found in the outermost energy level of an atom and that determines the atom’s chemical properties.

• The atoms of each element within a group on the periodic table have the same number of valence electrons.

Chemical BondingChapter 8

Valence Electrons

To Bond or Not to Bond

• The number of valence electrons determines if an atom will form bonds.

• The outermost energy level of an atom is full if the level contains eight electrons.

• Atoms of some elements need only two electrons to fill their outermost level.

To Bond or Not to Bond, continued

• Atoms that have eight electrons in their outermost level are nonreactive. So, they do not form bonds.

• Atoms that have fewer than eight valence electrons usually form bonds.

Section 2 Ionic BondsChapter 8

Bellringer

Compounds that contain ionic bonds, including common table salt, are called salts. Brainstorm uses for salts, things that contain salts, or words and phrases containing the word salt.

Record your ideas in your Science Journal.

What You Will Learn

• Ions of different elements can combine by forming ionic bonds.

• Positive ions and negative ions form when atoms lose or gain electrons.

• Ionic compounds form solids by building up a repeating pattern called a crystal lattice.

Forming Ionic Bonds

• An ionic bond forms when valence electrons are transferred from one atom to another atom.

• In an ionic bond, one atom has lost electrons and the other atom has gained electrons.

• An atom is neutral when the number of electrons equals the number of protons.

Forming Ionic Bonds, continued

• Ions are charged particles that form when atoms gain or lose electrons.

• If an ion has more protons than electrons, it is a positive ion.

• If an ion has more electrons than protons, it is a negative ion.

Ionic Bonding

Forming Positive Ions

• During chemical changes, the atoms that lose electrons form positive ions because these atoms have more protons than electrons.

• Because atoms of most metals have few electrons in their outermost energy level, metal atoms tend to lose valence electrons and form positive ions.

Forming Positive Ions, continued

• Energy is needed to remove electrons from atoms.

• The elements in Groups 1 and 2 react very easily because the energy needed to remove electrons from their atoms is so small.

Forming Negative Ions

• During chemical changes, the atoms that gain electrons form negative ions because there are more negative charges than positive charges.

• Because the outermost energy level of nonmetal atoms is almost full, the atoms of nonmetals tend to gain electrons and form negative ions.

Forming Negative Ions, continued

• The name of the negative ion that is formed usually ends with –ide.

• Energy is released when most nonmetal atoms gain electrons.

• The more easily an atom gains an electron, the more energy the atom releases.

Forming Ionic Compounds

• When ionic bonds form, the opposite charges of the ions cause the ions to stick together. But the compound formed is neutral because the charges cancel each other.

• When a metal and a nonmetal combine by ionic bonding, the resulting compound has different properties than the metal and nonmetal did.

Ionic Compounds

• The ions that make up an ionic compound are bonded in a repeating three-dimensional pattern called a crystal lattice. The crystal lattice is built up so that the positive ions are nearest to the negative ions, forming a solid.

• Ionic compounds are brittle and highly soluble, with high melting and boiling points.

Section 3 Covalent and Metallic BondsChapter 8

Bellringer

Examine the drawings of an oxygen atom and two hydrogen atoms. Each model shows the arrangement of electrons in the atom.

In your Science Journal, create a drawing that shows how these three atoms can be arranged to give each atom a full outer energy level. What kind of molecule have you drawn?

What You Will Learn

• Covalent compounds form when atoms of elements share electrons.

• Molecules are particles of covalent compounds and can be simple or complex.

• Atoms of metals are held together by metallic bonds.

• Metallic bonding gives metals certain properties.

Covalent Bonds

• A covalent bond forms when atoms share one or more pairs of electrons. Most things around you are held together by covalent bonds.

• Covalently bonded atoms form a particle called a molecule. A molecule is the smallest particle of a compound that has the chemical properties of the compound.

Covalent Bonds, continued

• An electron-dot diagram is a model that shows only the valence electrons in an atom.

• Electron-dot diagrams can help you predict how atoms might bond.

Covalent Compounds and Molecules

• Molecules made up of two atoms are called diatomic molecules.

• Elements that are found in nature as diatomic molecules are called diatomic elements.

• In a molecule of any diatomic element, the shared electrons are counted as valence electrons for each atom.

Metallic Bonds

• A metallic bond is a bond formed by the attraction between positively charged metal ions and the electrons in the metal. Positively charged metal ions form when metal atoms lose electrons.

• Metallic bonds extend throughout the metal in all directions because the outermost energy levels of the atoms overlap. So, valence electrons are free to move throughout the metal.

Metallic Bonds

Properties of Metals

• Metallic bonding allows metals to conduct electric current. Electrons move within a wire because the valence electrons are free to move throughout the metal.

• Because electrons move freely around metal ions, the atoms in metals can be rearranged. As a result, metals can be reshaped.

Properties of Metals, continued

• The properties of ductility and malleability describe a metal’s ability to be reshaped.

• Metal objects can be bent without being broken because electrons constantly moving around and between the metal ions maintain the metallic bonds no matter how the shape of the metal changes.

Chapter 8 Chemical Bonding

Use the terms below to complete the concept map on the next slide.

covalent bonds

molecules

electrons

metallic bonds

chemical bonds

Concept Map

Chemical Bonding Chapter 8

End of Chapter 8 Show

Chapter 8 Standards Assessment

1. Choose the appropriate form of the word constituent for the following sentence: “The compound has properties that differ from the properties of the elements that _____ it.”

A. constituent

B. constituting

C. constitute

D. constitutes

1. Choose the appropriate form of the word constituent for the following sentence: “The compound has properties that differ from the properties of the elements that _____ it.”

A. constituent

B. constituting

C. constitute

D. constitutes

2. Which of the following words means “the make up of parts of a whole”?

A. structure

B. ion

C. bond

D. constituent

2. Which of the following words means “the make up of parts of a whole”?

A. structure

B. ion

C. bond

D. constituent

3. Which of the following words is the closest in meaning to the word chemical?

A. poison

B. artificial

C. property

D. substance

3. Which of the following words is the closest in meaning to the word chemical?

A. poison

B. artificial

C. property

D. substance

4. Which of the following words means “to pick out”?

A. discuss

B. identify

C. review

D. analyze

4. Which of the following words means “to pick out”?

A. discuss

B. identify

C. review

D. analyze

5. Which of the following is closest in meaning to the word compound?

A. partner

B. fabrication

C. combination

D. recipe

5. Which of the following is closest in meaning to the word compound?

A. partner

B. fabrication

C. combination

D. recipe

6. A _____ forms when atoms share one or more pairs of electrons.

A. covalent bond

B. ionic bond

C. valence electron

D. nonmetal ion

6. A _____ forms when atoms share one or more pairs of electrons.

A. covalent bond

B. ionic bond

C. valence electron

D. nonmetal ion

7. Ionic bonds form when atoms pull electrons away from other atoms. If an atom loses electrons, what is the charge of the resulting ion?

A. negative

B. positive

C. neutral

D. unchanged

7. Ionic bonds form when atoms pull electrons away from other atoms. If an atom loses electrons, what is the charge of the resulting ion?

A. negative

B. positive

C. neutral

D. unchanged

8. The ions that make up an ionic compound are bonded in a repeating three-dimensional pattern. What is this pattern called?

A. chloride lattice

B. covalent lattice

C. crystal lattice

D. crystal pattern

8. The ions that make up an ionic compound are bonded in a repeating three-dimensional pattern. What is this pattern called?

A. chloride lattice

B. covalent lattice

C. crystal lattice

D. crystal pattern

9. The diagram below represents an oxygen atom. How many more valence electrons does the oxygen atom need to fill its outermost energy level?

10. What is a molecule?

A. the smallest particle of a substance that cannot be broken down any further by chemical reaction

B. a particle that forms when atoms gain or lose electrons

C. matter of particular or definite chemical composition

D. the smallest unit of a substance that keeps the physical and chemical properties of the substance

10. What is a molecule?

A. the smallest particle of a substance that cannot be broken down any further by chemical reaction

B. a particle that forms when atoms gain or lose electrons

C. matter of particular or definite chemical composition

D. the smallest unit of a substance that keeps the physical and chemical properties of the substance

11. Atoms of elements in _____ of the periodic table rarely form chemical bonds.

A. Group 1

B. Group 9

C. Group 17

D. Group 18

11. Atoms of elements in _____ of the periodic table rarely form chemical bonds.

A. Group 1

B. Group 9

C. Group 17

D. Group 18

Use the diagram below to answer the next question.

12. How many electrons are in the second energy level of the atom represented in the above diagram?

13. Which of the following sentences best describes electrons in relation to energy levels?

A. Electrons can be found in and between energy levels.

B. Electrons have definite energies, and they do not exist between energy levels.

C. Electrons exist inside the nucleus at definite energy levels.

D. Electrons can have an exact path within an energy level.

13. Which of the following sentences best describes electrons in relation to energy levels?

A. Electrons can be found in and between energy levels.

B. Electrons have definite energies, and they do not exist between energy levels.

C. Electrons exist inside the nucleus at definite energy levels.

D. Electrons can have an exact path within an energy level.

14. Protons are always found in the nucleus of an atom. What is the number of protons in the nucleus of an atom called?

A. atomic number

B. atomic mass

C. mass number

D. atomic mass unit

14. Protons are always found in the nucleus of an atom. What is the number of protons in the nucleus of an atom called?

A. atomic number

B. atomic mass

C. mass number

D. atomic mass unit

15. In the periodic table, elements that have similar properties are organized into vertical groups. The element argon is located in the group of elements known as the

A. alkali metals.

B. halogens.

C. noble gases.

D. transition metals.

15. In the periodic table, elements that have similar properties are organized into vertical groups. The element argon is located in the group of elements known as the

A. alkali metals.

B. halogens.

C. noble gases.

D. transition metals.

16. Which of the following is generally true of an element?

A. It cannot be melted into a liquid.

B. It has a characteristic density.

C. It conducts electric current.

D. It can be broken down into a simpler substance.

16. Which of the following is generally true of an element?

A. It cannot be melted into a liquid.

B. It has a characteristic density.

C. It conducts electric current.

D. It can be broken down into a simpler substance.

Chapter 8

phys. sci ch 8

number of electrons

chemical bonds form

chemical bonding section

atoms form bonds

number of valence electrons

ionic bonds chapter

ionic bonds section

atoms chemical properties

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