Covalent Bonding EQ: How are the chemical formulas and chemical names written for covalent molecules? How do you draw VSEPR diagrams for covalent compounds? What are the names and bonding/lone pairs for each molecular shape?

DAY 1

Review of Ionic Bonding Ionic bonds occur between a metal and a nonmetal, or between a positively charged particle and a negatively charged particle. Ionic bonds involve a transfer of electrons. Can you identify which of the following are joined by ionic bonds? NaCl - K3N - MgBr2 CO2 - N2 - Al2O3

Covalent Compounds Now, you will learn about another type of bond in which electrons are shared Covalent Bonds are atoms held together by SHARING electrons between NONMETALS

Covalent Bonding Covalent bonds occur between two nonmetals. A molecule is formed when two or more atoms bond covalently. Covalent bonds involve sharing of electrons.

Covalent “Molecules” A group of atoms joined together by a covalent bond is called a MOLECULE A compound is a group of two or more elements bonded together (Ionic or Covalent).

Ionic vs Covalent

Diatomic Molecules Certain elements occur in nature as diatomic molecules and not as single atoms (more stable as the molecule) Examples: H2, N2, O2, F2, Cl2, Br2, I2 Diatomic Molecules are bonded together by covalent bonds. THE SUPER 7!!!

Molecular Formulas The Molecular Formula is the formula of a molecular compound It shows how many atoms of each element a molecule contains Example H2O contains 3 atoms (2 atoms of H, 1 atom of O) C2H6 contains 8 atoms (2 atoms of C, 6 atoms of H)

Practice How many atoms total and of each do the following molecular compounds contain? H2 CO CO2 NH3 C2H6O

Practice: True or False All molecular compounds are composed of atoms of two or more elements. All compounds are molecules. Covalent compounds are composed of two or more nonmetals. Atoms in covalent compounds exchange electrons.

Naming Molecular Compounds The first element written in the formula is always written first, using the element name. The second element is named using the root of the element and the suffix “-ide”. Prefixes are used to indicate the number of atoms of each type that are present in the compound. Exception: Do not use the prefix mono- for the first element Drop the final letter of the prefix when the element name begins with a vowel

Table 1: Common Prefixes Used in Covalent Compounds Number of atoms Prefix 1 Mono- 6 Hexa- 2 Di- 7 Hepta- 3 Tri- 8 Octa- 4 Tetra- 9 Nona- 5 Penta- 10 Deca-

Naming Carbon dioxide CO2: ________________________________ SO2: ________________________________ S2O3: _______________________________ N2O: _______________________________ PCl5: ________________________________ Sulfur dioxide Disulfur trioxide Dinitrogen monoxide Phosphorous pentachloride

Formula Writing Selenium hexafluoride: ___________ Disilicon hexabromide: __________ Diboron monosilicide: __________ Iodine pentafluoride: ________ Hexaboron monosilicide: ________ SeF6 Si2Br6 B2Si IF5 B6Si

Covalent Compound Lewis Structures Lewis structures show how valence electrons are arranged among atoms in a molecule. Lewis structures show each element with 8 valence electrons (want to achieve 8 valence just like their closest noble gas) EXCEPTIONS: Hydrogen (H) only wants 2 Beryllium (Be) only wants 4 Boron (B) only wants 6 Shared electron pairs are covalent bonds and can be represented by two dots (:) or by a single line ( - )

Single, double, & triple bonds!!! F2 O2 N2

Completing a Lewis Structure EXAMPLE: CH3Cl 1. Add up available valence electrons: C = _____ H3 = ______ Cl = _____ Total = _____ **Each atom should have 8 ve- 2. Lewis Structure MUST be symmetrical Single bonds FIRST and fill the octet of outer atoms Then fill octet of inner atom 5. If you run out of valence electrons then you must add bonds!

Completing a Lewis Structure EXAMPLE: NBr3 1. Add up available valence electrons: N = _____ Br3 = ______ Total = _____ **Each atom should have 8 ve- 2. Lewis Structure MUST be symmetrical Single bonds FIRST and fill the octet of outer atoms Then fill octet of inner atom 5. If you run out of valence electrons then you must add bonds!

Learning Check CH4 2. SO3 C = H4 = ________ Total = S = O3 = ________