The Covalent Bond Pages

Learning Objectives Apply the octet rule to atoms that form covalent bonds. Describe the formation of single, double, and triple covalent bonds.

Review-Numbered Heads Together 1.I will ask a review question. 2.You will write your answer down on a whiteboard. Turn you board over when you have an answer. 3.When I give you the signal, everyone will stand up and share and discuss your answer with your team. 4.When EVERYONE knows the answer, you will erase your answers and sit down.

Review What is the octet rule? – Atoms lose, gain, or share electrons in order to acquire the stable electron configuration of a noble gas What is a valence electron? – Electrons in an atom’s outermost orbitals

Covalent Bond A covalent bond is a chemical bond formed through the sharing of one or more pairs of electrons between atoms. A molecular compound (or molecule) is a compound in which atoms are joined through covalent bonds.

Comparing Covalent and Ionic Bonds Ionic Bonds Form between a metal and nonmetal Electrons transferred Basic structural unit – formula unit Solids at room temp If soluble in water, forms an aqueous solution that conducts electricity Covalent Bonds Form between similar or even identical atoms, usually two nonmetals Electrons shared Basic structural unit – molecule May be solids, liquids, or gases at room temp If soluble in water, usually produces non-conducting aqueous solution

Diatomic Molecules A diatomic molecule is a molecule composed of two atoms. Nitrogen (N 2 ), fluorine (F 2 ), iodine (I 2 ), chlorine (Cl 2 ), bromine (Br 2 ), and hydrogen (H 2 ) form diatomic molecules.

Single Covalent Bonds Single covalent bond - one pair of electrons is shared between two atoms Group 17 elements form single-covalent bonds (fluorine molecule F 2 ) Group 16 elements share two electrons and form two bonds (water – H 2 O) Group 15 elements form three bonds with atoms of nonmetals (ammonia - NH 3 ) Group 14 form four covalent bonds (methane - CH 4 )

Multiple Covalent Bonds Double covalent bond - two atoms share two pairs of electrons Triple covalent bond – two atoms share three pairs of electrons

Valence Electrons and Number of Covalent Bonds Formed Not all elements can form double or triple covalent bonds. The number of bonds an element can form depends on how many electrons it needs to have a complete octet.

Valence Electrons and Number of Covalent Bonds Formed Elements that need electrons to complete an octet can form multiple covalent bonds (double or triple bonds) OR multiple single bonds. When more than one “behavior” is possible, the “bonding behavior” is determined by the element or elements to which it is bonded.O N N NCC

Summary Covalent bonds form when atoms share one or more pairs of electrons. Sharing one pair, two pairs, and three pairs of electrons forms single, double, and triple covalent bonds, respectively.

Notes Review 1.What is a covalent bond? 2.What is a molecular compound? 3.What are three differences between an ionic bond and a covalent bond (there are 5). 4.What is a diatomic molecule? 5.What are the 6 elements that form diatomic molecules?

Notes Review 5.What is the difference between a single, double, and triple covalent bond? 6.How many bonds do elements in groups 14, 15, 16, and 17 tend to form? 7.How can you use what you know about the octet rule and valence electrons to determine how many bonds an element will form?