Chapter 7 Ionic Compounds and Metals
National Standards for Chapter 7 • UCP.1 – Systems, order, and organization • UCP.2 – Evidence, models, and explanation • A.1 –Abilities necessary to do scientific inquiry • B-1 – Structure of atoms • B-2 – Structure and properties of matter • B-3 – Chemical reactions • B-4 – Motions and forces • B-6 – Interactions of energy and matter • E-1 – Abilities of technological design • E-2 – Understandings about science and technology • G.2 – Nature of scientific knowledge
Vocabulary/Study Guide • Define each term using the Glossary • Either write on the handout, or use your own paper • This is due on Test Day, Wednesday, December 18
Section 1: Ion Formation National Standards: • UCP.1 – Systems, order, and organization • UCP.2 – Evidence, models, and explanation • A.1 –Abilities necessary to do scientific inquiry • B-1 – Structure of atoms • B-2 – Structure and properties of matter
Objectives – Section 1 • Define a chemical bond. • Describe the formation of positive and negative ions. • Relate ion formation to electron configuration. REVIEW VOCABULARY: • octet rule: atoms tend to gain, lose, or share electrons in order to acquire eight valence electrons • ionization energy: refers to how easily an atom loses an electron • electron affinity: indicates how much attraction an atom has for electrons
New Vocabulary • chemical bond • cation • anion • Ions are formed when atoms gain or lose valence electrons to achieve a stable octet electron configuration.
Valence Electrons and Chemical Bonds • A chemical bond is the force that holds two atoms together. • Chemical bonds form by the attraction between the positive nucleus of one atom and the negative electrons of another atom.
Valence Electrons and Chemical Bonds • Atom’s try to form the octet—the stable arrangement of eight valence electrons in the outer energy level—by gaining or losing valence electrons.
Positive Ion Formation • A positively charged ion is called a cation. • This figure illustrates how sodium loses one valence electron to become a sodium cation.
Positive Ion Formation • Metals are reactive because they lose valence electrons easily.
Positive Ion Formation • Transition metals commonly form 2+ or 3+ ions, but can form greater than 3+ ions. • Other relatively stable electron arrangements are referred to as pseudo-noble gas configurations.
Negative Ion Formation • An anionis a negatively charged ion. • The figure shown here illustrates chlorine gaining an electron to become a chlorine ion.
Negative Ion Formation • Nonmetal ions gain the number of electrons required to fill an octet. • Some nonmetals can gain or lose electrons to complete an octet.
Math Transparency 7: Calculating Number of Electrons and Predicting Ionic Change
Homework, Section 1 • SECTION 1 REVIEW, Page 209 • Questions #1-6 • Answer with complete sentences • Due tomorrow
Section 2: Ionic Bonds and Ionic Compounds National Standards: • UCP.1 – Systems, order, and organization • UCP.2 – Evidence, models, and explanation • B-1 – Structure of atoms • B-2 – Structure and properties of matter • B-3 – Chemical reactions • B-4 – Motions and forces • B-6 – Interactions of energy and matter
Objectives – Section 2 • Describethe formation of ionic bonds and the structure of ionic compounds. • Generalizeabout the strength of ionic bonds based on the physical properties of ionic compounds. • Categorizeionic bond formation as exothermic or endothermic. Review Vocabulary: • compound:a chemical combination of two or more different elements
New Vocabulary • ionic bond • ionic compound • crystal lattice • electrolyte • lattice energy • Oppositely charged ions attract each other, forming electrically neutral ionic compounds.
Formation of an Ionic Bond • The electrostatic force that holds oppositely charged particles together in an ionic compound is called an ionic bond. • Compounds that contain ionic bonds are called ionic compounds. • Binary ionic compounds contain only two different elements—a metallic cation and a nonmetallic anion.
Properties of Ionic Compounds • Positive and negative ions exist in a ratio determined by the number of electrons transferred from the metal atom to the non-metal atom. • The repeating pattern of particle packing in an ionic compound is called an ionic crystal.
Properties of Ionic Compounds • The strong attractions among the positive and negative ions result in the formation of the crystal lattice. • A crystal latticeis the three-dimensional geometric arrangement of particles, and is responsible for the structure of many minerals.
Properties of Ionic Compounds • Melting point, boiling point, and hardness depend on the strength of the attraction.
Properties of Ionic Compounds • In a solid, ions are locked into position and electrons cannot flow freely—solid ions are poor conductors of electricity. • Liquid ions or ions in aqueous solution have electrons that are free to move, so they conduct electricity easily. • An ion in aqueous solution that conducts electricity is an electrolyte.
Properties of Ionic Compounds • This figure demonstrates how and why crystals break when an external force is applied.
Energy and the Ionic Bond • Reactions that absorb energy are endothermic. • Reactions that release energy are exothermic.
Energy and the Ionic Bond • The energy required to separate 1 mol of ions in an ionic compound is referred to as the lattice energy. • Lattice energy is directly related to the size of the ions that are bonded.
Energy and the Ionic Bond • Smaller ions form compounds with more closely spaced ionic charges, and require more energy to separate. • Electrostatic force of attraction is inversely related to the distance between the opposite charges. • The smaller the ion, the greater the attraction.
Energy and the Ionic Bond • The value of lattice energy is also affected by the charge of the ion.
Data Analysis Lab: Interpret Data, page 216 • Can embedding nanoparticles of silver into a polymer give the polymer antimicrobial properties?
Homework, Section 2 • SECTION 2 REVIEW, Page 217 • Questions #12-18 • Answer with complete sentences • Due tomorrow
Section 3: Names and Formulas for Ionic Compounds National Standards: • UCP.1 – Systems, order, and organization • UCP.2 – Evidence, models, and explanation • B-2 – Structure and properties of matter • E-2 – Understandings about science and technology • G.2 – Nature of scientific knowledge
Objectives – Section 3 • Relatea formula unit of an ionic compound to its composition. • Writeformulas for ionic compounds and oxyanions. • Applynaming conventions to ionic compounds and oxyanions. Review Vocabulary: • nonmetal:an element that is generally a gas or a dull, brittle solid and is a poor conductor of heat and electricity
New Vocabulary • formula unit • monatomic ion • oxidation number • polyatomic ion • oxyanion • In written names and formulas for ionic compounds, the cation appears first, followed by the anion.
Formulas for Ionic Compounds • Chemists around the world need to communicate with one another, so a standardized system of naming compounds was developed. • When writing names and formulas for ionic compounds, the cation appears first followed by the anion.
Formulas for Ionic Compounds • The chemical formula for an ionic compound, called a formula unit, represents the simplest ratio of the ions involved. • For example, the formula unit of magnesium chloride is MgCl₂ because the magnesium and chloride ions exist in a 1:2 ratio
Formulas for Ionic Compounds • Binary ionic compounds are composed of positively charged monatomic ions of a metal and negatively charged monatomic ions of a nonmetal • Monatomic ions are one-atom ions, such as Mg²+ or Br-.
Formulas for Ionic Compounds • Using Table 7: • What is the formula for the Beryllium ion? • The iodide ion? • The nitride ion? • Transition metals – groups 3 through 12 – and groups 13 & 14 are not included in Table 7 because of the variance in ionic charges of atoms in these groups • These groups can form several different positive ions
Formulas for Ionic Compounds • The charge of a monatomic ion is equal to its oxidation number, or oxidation state • Oxidation number, or oxidation state, is the charge of a monatomic ion. • Most transition metals and groups 13 & 14 have more than one possible ionic charge
Formulas for Ionic Compounds • The oxidation number of an element in an ionic compound equals the number of electrons transferred from the atom to form the ion • For example, in NaCl, the oxidation number of sodium is 1+ and the oxidation number of chlorine is 1-
Formulas for Ionic Compounds • The symbol for the cation is always written first, followed by the symbol of the anion. • Subscripts represent the number of ions of each element in an ionic compound. • If no subscript is written, it is assumed to be 1 • The total charge must equal zero in an ionic compound. • To determine the formula unit for Sodium fluoride, write the symbol and charge for each ion. • The ratio of ions in a formula unit of the compound must show that the number of electron lost by the metal equals the number of electrons gained by the non-metal.
Formulas for Ionic Compounds • Practice Problems #19-23, page 221
Formulas for Ionic Compounds • Polyatomic ionsare ions made up of more than one atom. • A polyatomic ion acts as an individual ion in a compound and its charge applies to the entire group of atoms • Since polyatomic ions exist as a unit, never change subscripts of the atoms within the ion. If more than one polyatomic ion is needed, place parentheses around the ion and write the appropriate subscript outside the parentheses.