Chapter 7: Ionic Compounds and Metals

Transcription

1 Chapter 7: Ionic Compounds and Metals Section 7.1 Section 7.2 Section 7.3 Section 7.4 Ion Formation Ionic Bonds and Ionic Compounds Names and Formulas for Ionic Compounds Metallic Bonds and the Properties of Metals Objectives Define a chemical bond. Describe the formation of positive and negative ions. Relate ion formation to electron configuration. Describe the formation of ionic bonds and the structure of ionic compounds. Generalize about the strength of ionic bonds based on the physical properties of ionic compounds. Categorize ionic bond formation as exothermic or endothermic. Relate a formula unit of an ionic compound to its composition. Write formulas for ionic compounds and oxyanions. Apply naming conventions to ionic compounds and oxyanions. Describe a metallic bond Relate the electron sea model to the physical properties of metals. Define alloys, and categorize them into two basic types. Review Vocabulary octet rule compound nonmetal physical property New Vocabulary chemical bond cation anion ionic bond ionic compound crystal lattice electrolyte lattice energy formula unit monatomic ion oxidation number polyatomic ion oxyanion electron sea model delocalized electron metallic bond alloy Section 7.1 Ion Formation Valence Electrons and Chemical Bonds A chemical bond is the force that holds two atoms. Chemical bonds form by the attraction between the of one atom and the of another atom. 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.

2 Positive Ion Formation A positively charged ion is called a. This figure illustrates how sodium loses one valence electron to become a sodium cation. Metals are reactive because they valence electrons easily. Transition metals commonly form 2+ or 3+ ions, but can form greater than 3+ ions. Other relatively stable electron arrangements are referred to as gas configurations. Negative Ion Formation An anion is a charged ion. The figure shown here illustrates chlorine gaining an electron to become a chlorine ion.

3 Nonmetal ions gain the number of electrons required to fill an octet. Some nonmetals can gain or lose electrons to complete an octet. Section 7.2 Ionic Bonds and Ionic Compounds Formation of an Ionic Bond The electrostatic force that holds oppositely charged particles together in an ionic compound is called an. Compounds that contain ionic bonds are called. Binary ionic compounds contain only two different elements a metallic cation and a nonmetallic anion.

4 Properties of Ionic Compounds Positive and negative ions exist in a determined by the number of transferred from the metal atom to the non-metal atom. The repeating pattern of particle packing in an ionic compound is called an. The strong attractions among the ions result in the formation of the crystal lattice. A is the three-dimensional geometric arrangement of particles, and is responsible for the structure of many minerals. Melting point, boiling point, and hardness depend on the strength of the attraction. In a solid, ions are locked into position and electrons cannot flow freely solid ions are of electricity. Liquid ions or ions in aqueous solution have electrons that are, so they conduct electricity easily. An ion in aqueous solution that conducts electricity is an electrolyte. This figure demonstrates how and why crystals break when an external force is applied. Energy and the Ionic Bond Reactions that absorb energy are Reactions that release energy are 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. 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 The value of lattice energy is also affected by the charge of the ion.

5 Formulas for Ionic Compounds When writing names and formulas for ionic compounds, the cation appears followed by the anion. Chemists around the world need to communicate with one another, so a standardized system of naming compounds was developed. A formula unit represents the simplest ratio of the ions involved. Monatomic ions are one-atom ions. Oxidation number, or oxidation state, is the of a monatomic ion The symbol for the cation is always written first, followed by the symbol of the anion. represent the number of ions of each element in an ionic compound. The total charge must equal zero in an ionic compound. ions are ions made up of more than one atom. 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 around the ion and write the appropriate subscript outside the parentheses.

6 Names for Ions and Ionic Compounds An is a polyatomic ion composed of an element (usually a non-metal), bonded to one or more oxygen atoms. Chemical nomenclature is a systematic way of naming compounds. Name the cation followed by the anion. For monatomic cations use the element name. For monatomic anions, use the root element name and the suffix ide. To distinguish between different oxidation states of the same element, the oxidation state is written in parentheses after the name of the cation. When the compound contains a polyatomic ion, name the cation followed by the name of the polyatomic ion.

7 Section 7.4 Metallic Bonds and the Properties of Metals Metals are but share several properties with ionic compounds. Metals also form lattices in the solid state, where 8 to 12 other atoms closely surround each metal atom. Within the crowded lattice, the outer energy levels of metal atoms. The electron sea model proposes that all metal atoms in a metallic solid contribute their valence electrons to form a. The electrons are free to move around and are referred to as electrons, forming a metallic cation. A metallic bond is the attraction of an metallic cation for delocalized electrons. Boiling points are much higher than melting points because of the energy required to separate atoms from the groups of cations and electrons.

8 Metals are because they can be hammered into sheets. Metals are because they can be drawn into wires. Mobile electrons surrounding positively charged nuclei make metals good conductors of. As the number of delocalized electrons, so does hardness and strength. Metal Alloys An is a mixture of elements that has metallic properties. Ex. Stainless steel, brass, cast iron The properties of alloys differ from the elements they contain. Ex. Steel is iron mixed with at least one other element. Some properties of iron are present, like magnetism, but steel is stronger than iron. are formed when some atoms in the original metallic solid are replaced by other metals of similar atomic structure. are formed when small holes in a metallic crystal are filled with smaller atoms.