Ionic Compounds and Metals. Chemistry Matter and Change: Chapter 7. BIG IDEA. Atoms in ionic compounds are held together by chemical bonds formed by the attraction of oppositely charged ions. 7.1 Ion Formation. 7.1 Main Idea.
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Ionic Compounds and Metals Chemistry Matter and Change: Chapter 7
BIG IDEA Atoms in ionic compounds are held together by chemical bonds formed by the attraction of oppositely charged ions.
7.1 Main Idea Ions are formed when atoms gain or lose valence electrons to achieve a stable octet electron configuration.
7.1 Objectives • Define a chemical bond. • Describe the formation of positive and negative ions • Relate ion formation to electron configuration.
Review Vocabulary & Concepts Ion Valence electron Octet Electron configuration Lewis-dot diagrams Electron affinity
New Vocabulary Chemical bond Ionic bond Cation Anion
Chemical Bond • The force that holds two atoms together • Three types • Ionic bonds *Chap 7 • Metallic bonds *Chap 7 • Covalent bonds *Chap 8
Valence Electrons and Chemical Bonds Each valence electron is represented as a dot around the nuclear core of the element.
Valence Electrons and Chemical Bonds • The most stable electron configuration for an element is the nearest noble gas. • ns2np6 • Octet • Ions gain or lose electrons to achieve noble gas configurations
Positive Ion Formation Cation: a positively charged ion Results when electrons are lost
Metal ions • Group 1 loses 1 electron +1 charge • Group 2 loses 2 electrons +2 charge • Group 13 loses 3 electrons +3 charge • Groups 3-12 usually lose 2 electrons Most have +2 charge (range from +1 to +3)
Negative Ion Formation Anion: negatively charged ion Formed when electrons are gained Non-metals
Nonmetal Ions • Group 15 gains 3 electrons 3- charge • Group 16 gains 2 electrons 2- charge • Group 17 gains 1 electron 1- charge
Section Summary A chemical bond is the force that holds two atoms together Some atoms gain or lose electrons to gain a stable configuration; these are called ions Most stable configurations end: ns2np6.
Can you… • Define a chemical bond. • Describe the formation of positive and negative ions • Relate ion formation to electron configuration.
7.2 Main Idea Oppositely charged ions attract each other forming electrically neutral ionic compounds.
7.2 Objectives 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 bonds Categorize ionic bond formation as exothermic or endothermic
Review Vocabulary & Concepts Compound Chemical bond Physical property Chemical property Electronegativity
New Vocabulary Ionic bond Ionic compound Crystal lattice Binary compound Electrolyte
Formation of an Ionic Bond • Electrons are exchanged between atoms • Increases stability of both • Ions are held together by the opposite charges
Definition of Ionic Bond • Bond formed between two elements with an electronegativity difference > 1.7 • Crystallize as sharply defined particles
Binary Ionic Compounds • Formed from a metal and a non-metal • Contain only two elements • Examoples • NaCl • MgO • CaCl2 • Fe2O3
Formation of Ionic Compounds • Net charge on all ions in a compound must be zero (0)! • More on this later!!!
Properties of Ionic Compounds Anion Cation Crystal Lattice: Highly organized crystal of cations and anions
Properties of Ionic Compounds Crystalline shape depends on the ions involved
Properties of Ionic Compounds • Physical properties • Very strong • Solid at normal temperatures • Very high melting point and boiling point • Many have brilliant colors due to transition metals • Hard, rigid • Brittle
Properties of Ionic Compounds • Conductivity (ability for electric charge to move through a substance • Solids have electrons locked in place • Non conductive • Aqueous solutions have easily moveable electrons • Electrolytes • Good conductors
Properties of Ionic Compounds PolarDissolution Dissolve in water May have radically different properties than the elements that compose them
Properties of Ionic Compounds Formation of lattice is always exothermic.
Section Summary Ionic compounds contain ionic bonds formed by the attraction of oppositely charged ions. Ions in an ionic compound are arranged in a repeating pattern called a lattice. Ionic compounds are electrolytes; they conduct electricity in liquid and aqueous states.
Can you… 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 bonds Categorize ionic bond formation as exothermic or endothermic
7.3 Big Idea In written names and formulas for ionic compounds, the cation appears first, followed by the anion.
7.3 Objectives • 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.
Review Vocabulary & Concepts Anion Cation Metal Non-metal
New Vocabulary Formula unit Monatomic ion Polyatomic ion Oxidation number Oxyanion
Describing Ionic Compounds Cl- Cl- Mg2+ • Formula unit- simplest way to indicate the composition of an ionic substance • NaCl • MgCl2
Monatomic Ions • Ions in which only one element is present • Na+, Cl-, Mg2+, P3-
Oxidation number • Fancy word for “charge” • aka oxidation state • Transition metals may have multiple oxidation states • Must tell the oxidation state • Ex: Iron 2+ is Iron II; Iron 3+ is Iron III
Formulas for Binary Ionic Compounds • CxAy • C is cation • A is anion • x number of cations in one unit • y is number of anions in one unit
Rules for writing formula units • CxAy • Cation is always first • Anion is always second • Net oxidation MUST BE ZERO
Tried and True Method Write out each ion. Place oxidation number under each ion Cross multiply Reduce to simplest form
Write out each ion. Sodium and chlorine Na Cl
Place oxidation number under each ion • Sodium and chlorine Na Cl +1 -1