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Resources Chapter Presentation Bellringers Image Bank Standards Assessment Visual Concepts Math Focus

Chemical Bonding Chapter 8 Table of Contents Section 1 Electrons and Chemical Bonding Section 2 Ionic Bonds Section 3 Covalent and Metallic Bonds

Section 1 Electrons and Chemical Bonding Chapter 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.

Section 1 Electrons and Chemical Bonding Chapter 8 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.

Section 1 Electrons and Chemical Bonding Chapter 8 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.

Section 1 Electrons and Chemical Bonding Chapter 8 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.

Section 1 Electrons and Chemical Bonding Chapter 8 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 Bonding Chapter 8

Chemical Bonding Chapter 8 Valence Electrons

Section 1 Electrons and Chemical Bonding Chapter 8 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.

Section 1 Electrons and Chemical Bonding Chapter 8 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 Bonds Chapter 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.

Section 2 Ionic Bonds Chapter 8 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.

Section 2 Ionic Bonds Chapter 8 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.

Section 2 Ionic Bonds Chapter 8 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.

Chemical Bonding Chapter 8 Ionic Bonding

Section 2 Ionic Bonds Chapter 8 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.

Section 2 Ionic Bonds Chapter 8 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.

Section 2 Ionic Bonds Chapter 8 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.

Section 2 Ionic Bonds Chapter 8 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.

Section 2 Ionic Bonds Chapter 8 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.

Section 2 Ionic Bonds Chapter 8 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 Bonds Chapter 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?

Section 3 Covalent and Metallic Bonds Chapter 8 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.

Section 3 Covalent and Metallic Bonds Chapter 8 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.

Section 3 Covalent and Metallic Bonds Chapter 8 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.

Section 3 Covalent and Metallic Bonds Chapter 8 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.

Section 3 Covalent and Metallic Bonds Chapter 8 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.

Chemical Bonding Chapter 8 Metallic Bonds

Section 3 Covalent and Metallic Bonds Chapter 8 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.

Section 3 Covalent and Metallic Bonds Chapter 8 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.

Chemical Bonding Chapter 8 Concept Map Use the terms below to complete the concept map on the next slide.

Chemical Bonding Chapter 8 Concept Map

Chemical Bonding Chapter 8 End of Chapter 8 Show

Standards Assessment Chapter 8 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

Standards Assessment Chapter 8 2. Which of the following words means “the make up of parts of a whole”? A. structure B. ion C. bond D. constituent

Standards Assessment Chapter 8 3. Which of the following words is the closest in meaning to the word chemical? A. poison B. artificial C. property D. substance

Standards Assessment Chapter 8 4. Which of the following words means “to pick out”? A. discuss B. identify C. review D. analyze

Standards Assessment Chapter 8 5. Which of the following is closest in meaning to the word compound? A. partner B. fabrication C. combination D. recipe

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