Chapter 5 Notes COMPOUNDS AND MOLECULES

Chemical Formulas  A chemical formula contains atomic symbols and subscripts to show the elements and the number of atoms of each element in a compound.  Ex: H 2 O, C 6 H 12 O 6, CH 4

How to read a chemical formula.  Each capital letter is a new element.  NaCl = Na + Cl (1 Na, 1 Cl)  Each subscript tells you how many of the element to the left there are. No subscript means only 1 of that element.  H 2 O = H 2 + O = H + H + O (2 H, 1 O)

What is a Compound ?  A compound is a pure substance that contains two or more elements.  Examples: Table Salt NaCl (Sodium and Chlorine) Water H 2 O (Hydrogen and Oxygen)

What is a Molecule ?  A molecule is a neutral particle that forms as a result of electron sharing.  Molecules form by Covalent Bonds.  Examples of molecules:  O 2 (Oxygen gas), H 2 O (Water), CO 2 (Carbon Dioxide)

Compound vs Molecule Compound  Made of 2 or more different elements.  Formed by ionic or covalent bonds. Molecule  Made of 2 or more atoms sharing electrons.  Formed by covalent bonds.

Covalent Bonds  A chemical bond formed when atoms share electrons Shared electrons

Covalent Bonds  Nonmetals combine with other nonmetals by sharing electron instead of gaining or losing electrons.  Sharing electrons is what forms covalent bonds.

Ionic Bonds  Ionic Bonds are an electrical attraction between 2 oppositely charged ions. Attracted to

Ionic Bonds  Ionic Bonds form between metals and non-metals.  Metals are elements to the left of the black staircase line on the periodic table.

Hydrogen is a NON-METAL!!! Metals   Non-Metals

Valence Electrons  Valence Electrons are the number of electrons in an atom’s outermost energy level.  Hydrogen has 1 valence electron.

How do you know how many valence electrons an element has?  It’s Easy!!!  Use a periodic table!!!  The number at the top of the column with an “A” tells you the number of valence electrons!  EX: 1A = 1 valence electron 2A = 2 valence electrons 6A = 6 Valence electrons

1 Exception : Helium only has 2 Valence Electrons # of Valence Electrons!!!

Lewis Dot Diagrams

 Lewis Dot Diagrams show the number of valence electrons an element has.

Steps to make a Lewis Dot Diagram  1. To make a Dot Diagram, begin by writing the chemical symbol of the element. Sodium = Na Oxygen = O  2. Next, look at the column number. (top of the periodic table) The number equals the number of dots you write around the symbol.  Ex: Group 1A = 1 dot Group 7A = 7 dots

 Now that you know how many dots, draw them around your element symbol following this rule.  3. Go around the symbol top, right, bottom, left. Each side needs 1 dot before you can add a second dot to the side. Sodium has 1 dot. Na Oxygen has 6 dots O

NOW YOU TRY!!!  Draw the Dot Diagrams for the following Elements:  Nitrogen  Magnesium  Lead  Iodine

 Draw the Dot Diagrams for the following Elements:  Nitrogen  Magnesium  Lead Pb  Iodine

Combining Atoms

Covalent Bonds (A Review!)  Nonmetals combine with other nonmetals by sharing electrons instead of gaining or losing electrons.  Sharing electrons is what forms covalent bonds.

How can we figure out how many covalent bonds an atom can form? Lewis Dot Diagrams can help.. Or you can just memorize it. In the Dot Diagrams, any dot/electron by itself can form a covalent bond. 2 dots together are happy and will not form a covalent bond. O 2 Dots, so no covalent bonds. 1 Dot only, these sides can form covalent bonds

Drawing Covalent Bonds  The most common way to show a covalent bond between 2 atoms is to draw a line connecting the atoms. Covalent bond

Example Draw H 2 O showing the covalent bonds.  1 st, draw the dot diagrams  2 nd, connect single dots with lines.

There can be multiple bonds between 2 atoms! Double Bond Triple Bond

Draw NH 3  Draw NH 3

Draw NH 3

Metals, Crystals and Polymers

Metals  Properties of Metals  Shiny!  Conduct Heat and Electricity  Malleable (Can be squished into shapes without breaking)  Ductility (Can be squeezed into wires)

Crystals… yeah, they’re cool!

Properties of Crystals  Formed of repeating arrangements of atoms, ions or molecules.  In table salt, Sodium and Chlorine make a repeating pattern.

Polymers  A COVALENT compound made up of repeating units (Monomers) linked together like a chain.  Examples:

Fun group talking time!  In your group make a list of all the different metals, crystals and polymers you can think of. MetalsCrystalsPolymers Gold Silver ??? Salt ???