Chapter 8: Covalent Bonding Mr. Stripling Pre-AP Chemistry Room 402

Covalent Bonds Chemical bond that results from sharing valence electrons Forms a molecule Can form between elements that are near each other on the periodic table Most are between atoms of nonmetallic elements

Covalent Bond Formation Diatomic molecules (H2, O2, F2, Cl2, Br2, and I2) form when two atoms of each element share electrons One pair of electrons are covalently bonded (shared) and three pairs of electrons are lone pairs (not shared)

A chemical bond that results from sharing valence electrons? Most of these bonds are between atoms of what type of elements? H2, O2, F2, Cl2, Br2, and I2 are examples of what type of molecules?

Single Covalent Bonds When only one pair of electrons is shared Hydrogen m0lecule B and C represent Lewis structures

Group 17 and Single Bonds The halogens have 7 valence electrons Form single covalent bonds to form an octet Example: Fluorine from earlier

Group 16 and Single Bonds Atoms of group 16 can share two electron and form two covalent bonds

Group 15 and Single Bonds Group 15 elements form three covalent bonds with atoms of nonmetals

Group 14 and Single Bonds Atoms of group 14 form four covalent bonds

What is a covalent bond formed by one pair of electrons being shared? Group 16 elements can share how many electrons? Group 15 elements can form how many covalent bonds? Which group on the periodic table can form 4 covalent bonds?

Sigma Bond Single covalent bonds, represented by the Greek letter sigma ( ) Occur when orbitals of atoms overlap

Multiple Covalent Bonds Occurs when atoms share multiple pairs of electrons Double and triple bonds

Double Bonds Occur when two atoms share two pairs electrons

Triple Bonds Forms when three pairs of electrons are shared between two atoms

How many pairs of electrons are shared in a double covalent bond? How many electrons are shared in a triple bond?

Strength of Covalent Bonds Depends on distance between the bonded nuclei The shorter the bond length, the stronger the bond Single bonds < triple bonds

Bonds and Energy Energy changes occur when bonds between atoms form or break Energy is released when a bond forms Energy must be added to break a bond

Team Classwork Problems 1-6 on page 244 Problem 1 (a-d) on page 980 for Chapter 8

Naming Binary Molecular Compounds Made of nonmetal atoms (NOT metal atoms or ions) Example: dinitrogen monoxide (N2O) Naming rules: The first element in the formula is always named first, using the entire element name (nitrogen) The second element in the formula is named using its root and adding the suffix –ide (oxide) Prefixes are used to indicate the number of atoms of each element that are present in the compound (dinitrogen monoxide)

Exceptions to the rules The first element in the compound never uses the prefix mono- (CO is carbon monoxide, not monocarbon monoxide)

When naming a binary molecular compound, what part is named first? Which part of the formula is named using its root and adding the suffix –ide? The first element in the compound never uses which prefix? Name this binary covalent compound: S9F6

Common Names for Molecular Compounds Water = H2O = dihydrogen monoxide Ammonia = NH3 = nitrogen trihydride Nitric oxide = NO = nitrogen monoxide

Naming Binary Acids Binary acids contain hydrogen and one other element Example: hydrochloric acid (HCl) First word has the prefix hydro- to name the hydrogen part of the compound The rest of the first word consists of a form of the root of the second element plus the suffix –ic (HCl becomes hydrochloric) The second word is always acid

Binary acids can contain more that two elements As long as no oxygen is present in the acidic compound formula it is named as a binary acid The root of the second part of the name is the root of the polyatomic ion Example: HCN = hydrocyanic acid

Binary acids contain what? The rest of the first word of a binary acid consists of a form of the root of the second element plus what suffix? The first word of a binary acid contains what prefix? When naming a binary acid, what is the second word? Can binary acids contain more than two elements If oxygen is present, is it still a binary acid?

Naming Oxyacids Oxyacid – an acid that contains both a hydrogen atom and an oxyanion Oxyanion – a polyatomic ion containing one or more oxygen atoms

Identify the oxyanion present The first word of an oxyacid’s name consists of the root of the oxyanion and the prefix per- or hypo- if it is part of the oxyanion’s name If the oxyanions' name ends with the suffix –ate, replace it with the suffix –ic. If the name of the oxyanion ends with the suffix –ite, replace it with –ous Example: nitric acid (HNO3) NO3-, the nitrate ion becomes nitric The second word of the name is always acid

What is an acid that contains both a hydrogen atom and an oxyanion? What is a polyatomic ion containing one or more oxygen atoms? If the oxyanions' name ends with the suffix –ate, replace it with what suffix? If the name of the oxyanion ends with the suffix –ite, replace it with what suffix?

Team Classwork Problems 14-17 on page 249 Problems 19-23 on page 251