10/26 Opener Create a cohesive hypothesis from yesterday’s class notes. Be sure to include a rationale for your hypothesis (why). I will ask 5 people to share. Compare the reaction of sodium & water to sodium & chlorine gas. Why are the reactions so violent, but the products are stable? (Some you can eat!) 3rd Period Full shells Stability Ionization energy (Na) H energy Valence shell full 4th Period Stability Full valence shell Unstable stable Product non reactive

Ionic and Covalent Bonds S WBAT: Describe the formation of ionic & covalent compounds Describe the properties of ionic & covalent compounds

Formation of Ionic Compounds Ionic compounds are composed of cations and anions, usually a metal cation and nonmetal anion. Are electrically neutral

Ionic Bonds Electrostatic forces that hold ions together in ionic compounds are called ionic bonds Example: Sodium chloride has Na+1 and Cl- Their opposite charges attract each other and they “stick together”

Formula Units A chemical formula shows the kinds of elements and the number of each in a compound Example: NaCl, AlBr3, H2O A formula unit is the lowest whole-number ratio of ions in an ionic compound Example: 1:1, 1:3, 2:1 AlBr3 H2O NaCl

Properties of Ionic Compounds Crystalline Solids (at room temp) High Melting Point Conduct an electric current when melted or dissolved in water Made up of a metal and non metal Generally a brittle solid Most ionic compounds are crystalline solids at room temperature They have a regular repeating 3-D patterns Ionic compounds generally have high melting points

Octet Rule in Covalent Bonding When bonding an atom either gains or loses electrons to achieve the electron configuration of a noble gas In covalent bonding, atoms share electrons to attain the electron configuration of a noble gas

Properties of Covalent Compounds Generally insoluble in water Non conductive Can be solid, liquid, or gas Made up of non metals

Single Covalent Bonds Two atoms are held together by sharing a pair of electrons An electron dot structure represents the shared pair of electrons of the covalent bond by two dots. Ex: H:H

O H F – F Single Covalent Bonds A structural formula represents the covalent bonds by dashes and shows the arrangement of covalently bonded atoms. An unshared pair, or lone pair, is a pair of valence electrons that are not shared between atoms Examples: O H F – F

Double and Triple Covalent Bonds A double covalent bond involves two shared pair of electrons A triple covalent bond is formed by sharing three pairs of electrons Examples: :N N: O = C = O

Coordinate Covalent Bonds A coordinate covalent bond is a bond where one atom contributes both bonding electrons Examples: :C O: A polyatomic ion, like NH4+ , is a group of atoms with a positive or negative charge that behaves as a unit.

Resonance A resonance structure occurs when it is possible to draw two or more valid electron dot structures that have the same number of electron pairs in the molecule

Exceptions to the Octet Rule NO2 has a single unpaired electron on the N Phosphorus and sulfur can have 10 or 12 valence electrons sometimes

As a class What is an atom trying to do when it bonds? What is the difference between an ionic bond and a covalent bond What is an electron dot structure? If two atoms are bonded together, how do you show their dot structure?