Unit 2.1: Lewis Dot Structures and Ionic Bonding

Bell Work October 6 Bell Work: Agenda: Turn in Test Corrections and anything you forgot to turn in while I was gone Planner: No Homework Notes Lewis Dot Structure Activity Bell Work: Write down 2 things you learned while I was on Outdoor Ed. My Favorite Demonstration of All Time

Chemical Reactions When substances react and new substances form Chemical Bond: the force of attraction that holds two atoms together as a result of the rearrangement of electrons between them. When atoms bond, electrons may be transferred from one atom to another or shared between the atoms. Chemical Reactions are shown with chemical equations Chemical Reactions Video

Chemical Equations Show the rearrangement of atoms to form new substances in a chemical reaction Example: CH4 + 2O2  CO2 + 2H2O Reactants: The substances that react; what you start with (left side of arrow) Products: The substances that are produced; what you make (right side of arrow)

Reading a Chemical Equation CH4 + 2O2  CO2 + 2H2O CH4: Methane O2: Oxygen CO2: Carbon Dioxide H2O: Water “Methane and oxygen react to form carbon dioxide and water” + : “and”  : “react to form” Coefficients are the number of molecules of each substance

Valence Electrons Electrons in the outermost shell of an atom Atoms can give away, take away, or share electrons to get to 0 or 8 valence electrons Remember, they want an empty or full valence shell, if they don’t have one then they are unstable (HAPPY OCTOPUS!)

Lewis Dot Structures of Elements Lewis Dot structures are used to show valence electrons Can be helpful when predicting how elements bond Rules: Look on the periodic table to determine how many valence electrons are in an element Write the symbol of the element Imagine that the element is in a box with 4 sides Start on top and rotate clockwise putting one dot (electron) at a time Continue to circle, double electrons when needed. Do not add more than 2 electrons to each side

Write the Lewis Dot Structure for the following Elements: Lithium (Li): Aluminum (Al): Bromine (Br):

Bell Work October 7 Bell Work: P How many valence electrons do the following elements have? He Cl Ne H Li Agenda: Turn in Article and Article Summary Planner: Lewis Dot Structure of Ionic Compounds Lewis Dot Structure Activity Notes

Ions An Ion is a charged particle The number of electrons is NOT equal to the number of protons Atoms become charged particles when they gain or lose electrons

Cations and Anions Cations: Gained one or more electrons Lost one or more electrons Negatively Charged Positively Charged Non-metals form anions Metals form Cations Anions:

Naming Ions Cations: Anions: Name of Atom + Ion Stem of atom + ide Example: Sodium becomes Sodium Ion Fluorine become Fluoride Calcium becomes Calcium Ion Nitrogen becomes Nitride

What type of Ions do each group form? Remember, elements are lazy, they do whatever is easiest They want to either gain or lose electrons to get to 0 or 8 valence electrons Example: If I have 1-3 valence electrons, it is easier to lose electrons than to gain them If I have 5-7 valence electrons, it is easier to gain electrons than to lose them IF I have 4, I could go either way

Bell Work: Bell Work October 8 Label the following as a metal or a nonmetal. Label if it will form a cation or an anion. N Al F Li Agenda: Planner: Lewis Dot Structure of Ionic Compounds Notes Lewis Dot Structure of Ionic Compounds Lattice Structure Activity

Ionic Charges Atom gaining electrons = anion Adding a negatively charged particle makes the atom more negative Atoms losing electrons = cation Taking away an electron means you take away something that is negative. This makes the atom more positive Example: Negative people in your life will make you more negative If you get rid of this negative person, then you will be happier or more positive

Ions form Ionic Bonds Electrons are TRANSFERRED from one atom to another to form ions This creates a negatively charged ion (anion) and a positively charged ion (cation) Opposites attract, the anion is attracted to the cation, this creates an IONIC BOND Dogs Teach Bonding Video

Ions form Ionic Bonds Transfer of electrons from metals to nonmetals All Ionic Bonds are called “Salts” Ionic Bonds are weak, compared to other types of bonds Bond between METAL and NONMETAL

Lewis Dot Structures of Ionic Compounds Na + Cl K + F Be + I + I

Properties of Ionic Bonds Solubility: the ability to dissolve in a solvent (typically water, but can include other liquids such as alcohols) Conductivity: describes if a substance can carry electric current Melting Points: temperature at which compounds melt (Celsius)

Crystal Lattice Styrofoam Ball Activity Positive ions (cations) are attracted to negative ions (anions)

Solubility Solubility: Ability to dissolve in a solvent Insoluble: Not Soluble (Does not dissolve) Partially Soluble: Only partially dissolves Ionic compounds tend to dissolve well in water or alcohol but not in things like oil

Solubility When ionic compounds dissolve, they are pulled out of their lattice structure and into their ionic state Dissociation: when ionic compounds are pulled into their ions and out of their lattice structure Ionic Dissociation Animation

Conductivity Conductivity: The ability to conduct electricity Ionic compounds are not conductive in their solid state They are conductive in their liquid state because the ions are dissociated Aqueous: Dissolved in water Electrolyte an aqueous salt solution Conductivity Animation

Melting Point Melting Point (MP): temperature at which compounds melt Melting Points are extremely high for ionic compounds due to their lattice structure and the strength of their bond

Flame Test Metals turn a very specific color when exposed to flame if they are in an ionic compound Every metal has it’s own specific color You can identify an unknown metal by the color of the flame They use this for fireworks!