2 New Unit: Chemical Bonding Essential Questions: What are the processes by which different atoms come together to form new compounds and what forces hold solutions of these compounds/molecules together?
3 Ions An atom with a charge Positive: cation Negative: anion How do these atoms become charged?
4 Valence Electrons Electrons in the highest occupied energy level The number of valence electrons greatly determines chemical properties of an element and how it will reactHow can we find the number of valence electrons in an element?
5 By using electron configurations Electron configuration for chlorine: 1s22s22p63s23p5 What is the highest energy level reached? 3 How many electrons are there? 7
6 Because of trends, we can also use group numbers! Looking at the electron configuration for elements in the same group, they will all have the same number of valence electrons (just the A groups though! Not the B groups.)
7 Guided Practice on Valence Electrons How many valence electrons are there in the following elements? Chlorine Calcium Aluminum Carbon Neon
8 Electron Dot Structures Also known as Lewis StructuresDiagrams that represent the number of valence electrons in the atomFind number of valence electronsWrite element symbolFill valence electrons around symbol, one on each side first then double up
9 Guided Practice on Lewis Structures Find the Lewis Dot Structures for the following elements: Chlorine Calcium Aluminum Carbon Neon
10 Octet RuleNoble gases are the most stable elements on the Periodic Table due to the fact that they have 8 valence electrons (a complete outer shell)Atoms will either lose or gain electrons through bonding in order to attain those complete 8 configurationsMetal elements tend to lose electrons while nonmetals tend to gain
11 Forming ions How do cations form? How do anions form? Losing valence electronsWho tends to form cations?How do anions form?Gaining valence electronsWho tends to form anions?
16 Formation of Ionic Compounds Composed of a cation and an anionHeld together by ionic bondsRepresented by a chemical formulaA formula unit is the lowest whole-number ratio of ions in an ionic compound
17 Formation of Ionic Compounds When writing the formulas, use the criss-cross methodMg Cl-1MgCl2