Lewis Dot diagrams 1. Developing and using models to predict formulas for stable, binary ionic compounds based on balance of charges 1
Lewis Dot Diagrams Refresher Element symbol is the centerpiece, surrounded by dots Only focus on valence electrons Each dot represents 1 valence electron Start at the top and move clockwise DO NOT PAIR UNTIL YOU GET TO VE #5 These diagrams can be used to help us show chemical reactions when atoms bond together. Boron is in group 13, so it should only have 3 valence electrons. So cross of two VE on your model X X B Ca 2
Time to start exploring ionic bonds Some slides will require you to write and/or highlight information. Those I slides will be marked with a 3
I lost valence electron(s) I gained valence electron(s) Ions become charged by gaining or losing electrons 4
What is an ionic bond? An ionic bond occurs when valence electrons are completely transferred from one atom to another. Occurs between a metal and a nonmetal The metal becomes a cation and the nonmetal becomes an anion Why does the METAL become a cation? Why does the NONMETAL become an anion? 5
Binary Ionic Compounds Binary means we will be bonding TWO different elements together. Which of the following show binary compounds? (Circle all that apply on your copy.) Li O H O CO Al S 2 2 2 2 3 6
Chemical Formulas Now that we have selected all of the compounds, let s discuss how they are written Li 2 O H 2 O CO 2 Al 2 S 3 These are ALL chemical formulas. Chemical Formulas uses ELEMENT SYMBOLS and SUBSCRIPTS to tell us two things. 1) The type of elements in the compound 2) The # atoms of each element involved 7
Chemical Formulas Li 2 O Al 2 S 3 How many atoms of Lithium are present? How many atoms of Oxygen are present? How many atoms of Aluminum are present? How many atoms of Sulfur are present? 8
Reaction is another way of saying bonding The picture above shows an atom of Sodium transferring its valence electron to chlorine. This reaction results in the formation of a Sodium ion (Na+) and a Chlorine ion (Cl-). These ions are attracted to each other because of their opposite charges. The result is a called Sodium Chloride, a binary ionic compound. 9
How can Lewis Dot Diagrams (electron dot structures) help us MODEL chemical reactions? 10
Let s practice! Reactions - draw a picture showing each reaction, and name the ionic compound. 1) Lithium reacting with Fluorine yielding Lithium Fluoride Li + F LiF Lithium fluoride only needs one atom of each element to make a neutral compound. 11
Let s practice! Try drawing the Lewis dot model showing the chemical bond between Calcium and Oxygen. 2) How many atoms of Calcium do you need? How many atoms of Oxygen do you need? 12
Let s practice! Try drawing the lewis dot model showing the chemical bond between Calcium and Oxygen. 2) How many atoms of calcium do you need? How many atoms of oxygen do you need? 13
Let s practice! Try drawing the Lewis dot model showing the chemical bond between Beryllium and Fluorine. 3) How many atoms of beryllium do you need? How many atoms of fluorine do you need? Is this a binary compound? Justify your answer. 14
2. Use the IUPAC nomenclature for translating between chemical names and chemical formulas Binary ionic compounds Binary covalent compounds Containing main group elements & compounds 15
Naming Binary Ionic Compounds Metal is listed first You do not change this name at all. Nonmetal is listed second Drop the ending and add -ide Examples Magnesium Oxide 16