+ Lewis Dot Structures Wednesday, November 5 th C.3.1 Describe, compare, and contrast the characteristics of the interactions between atoms in ionic and covalent compounds. You Will Be Able To: Create electron dot diagrams based on the position of elements in the periodic table

+ Do Now 1. In a covalent bond, electrons are _____ a. Lost or gained b. Shared 2. When Lithium loses an electron, it gets charge of _____ a. -1 b. +1 c Magnesium Bromide is a _____ compound a. Metallic b. Covalent c. Ionic 4. Non-metals tend to _______ electrons to be come ________ ions in an ionic bond a. lose, positive b. gain, negative c. lose, neutral 5. Covalent bond is formed between atoms of ________ a. Metals b. Non metals c. Metals and nonmetals 6. How many valence electrons are in one atom of hydrogen? 7. How many valence electrons does hydrogen need to have a full first shell?

+ 1. In a covalent bond, electrons are _____ a. Lost or gained b. Shared

+ 2. When Lithium loses an electron, it gets charge of _____ a. -1 b. +1 c. 0

+ 3. Magnesium Bromide is a _____ compound a. Metallic b. Covalent c. Ionic

+ 4. Non-metals tend to _______ electrons to be come ________ ions in an ionic bond a. lose, positive b. gain, negative c. lose, neutral

+ 5. Covalent bond is formed between atoms of ________ a. Metals b. Non metals c. Metals and nonmetals

+ 6. How many valence electrons are in one atom of hydrogen? 1 7. How many valence electrons does hydrogen need to have a full first shell? 2

+ Ionic BondsVs.Covalent

+ Valence Electrons Valence electrons – electrons in an atom’s highest occupied energy level Outermost electrons of the electron cloud Establish chemical characteristics of elements Only electrons shown in Lewis electron dot structures Symbolized as dots

+ Electron Dot Structure A.K.A: Lewis dot structure Step 1 : Identify the symbol for the element and its number of valence electrons using the periodic table. Step 2: Place the corresponding number of electron dots around the symbol. Imagine that the symbol has four sides: top, right, bottom, and left. Begin by assigning one dot per side, moving clockwise around the symbol. Then, if there are still more dots to assign, start adding a second dot to each side until all of the valence electrons have been accounted for.

+ Drawing an Electron Dot Structure: Example Step 1 : Identify the symbol for the element and its number of valence electrons using the periodic table. The symbol for phosphorus is P. Phosphorus is in group 5A so it has 5 valence electrons. Step 2: Place the corresponding number of electron dots around the symbol. Imagine that the symbol has four sides: top, right, bottom, and left. Begin by assigning one dot per side, moving clockwise around the symbol. Then, if there are still more dots to assign, start adding a second dot to each side until all of the valence electrons have been accounted for.

+ Example 2 - Carbon 1. Write the symbol for the element. 2. How many valence electrons does it have? 3. Start on the top and draw the electrons clockwise or counter-clockwise around the element. 4. Check your work— did you draw the correct number of electrons? C

+ Practice Problems Draw the electron dot diagrams for the following elements: Chlorine Magnesium Neon Boron

+ Atoms in the same column/group/family will have the same electron dot diagram because they have the same number of valence electrons

+ Polyatomic Lewis Dot Structures Poly = many We can draw Lewis Dot structures for molecules to represent molecular structure It is important to keep in mind that the models we are discussing are just that…..models. We are operating under the assumption that when forming bonds, atoms “share” electrons using atomic orbitals. Electrons involved in bonding: “bonding pairs”. Electrons not involved in bonding: “lone pairs”

+ Central idea: the most stable arrangement of electrons is one in which all atoms have a “noble” gas configuration. Example: NaCl versus Na + Cl - Na: [Ne]3s 1 Electron pairs between atoms indicate bond formation.

+ Polyatomic Lewis Dot Structures 1. Sum the valence electrons for all atoms to determine the total number of electrons. 2. Use pairs of electrons to form a bond between each pair of atoms (bonding pairs). 3. Arrange remaining electrons around atoms (lone pairs) to satisfy the “octet rule” (“duet” rule for hydrogen).

Lewis Dot Structures An example: Cl 2 O 20 e - 16 e - left

Lewis Dot Structures An example: CH 4 8 e - 0 e - left Done!

Lewis Dot Structures An example: CO 2 16 e - 12 e - left 0 e - left Octet Violation CO double bond

Draw the LDS: PBr 3 H 2 S