Chapter 6 Section 2Pg. 165-169

Covalent Bonds

• Energy is _______ in the chemical bonds of sugar– Elements in ____: Carbon, Oxygen, and Hydrogen– All are nonmetals; transfer of electrons does ____

tend to occur between nonmetal atoms– So how are nonmetals able to form bonds?

Covalent Bonds

• You and a friend need a total of 10 dollars to buy some food. You have $6 and your friend has $4. Together you have $10, so in order to buy the food you may put your money together and share the food.

• When _______ join together, they display a similar ______ strategy

Covalent Bonds• Sharing Electrons– H atom has 1 electron, but if it had 2, it would

have the _____ electron configuration as He (therefore it would be ______)

– 2 H atoms can achieve a stable electron configuration by ______ their electrons and forming a _______ bond

– Covalent Bond- a chemical bond in which 2 atoms share a pair of valence electrons

– When 2 atoms share one pair of electrons, the bond is called a _____ ____

Covalent Bonds

Covalent Bonds• Molecules of Elements– Molecule- a neutral group of atoms that are joined

together by one or more _______ bonds– The attractions between the ____ electrons and

the protons in each nucleus hold the atoms together in a covalent bond

– Chemical ______ can be used: H molecule= H2

– Many nonmetal elements exist as _____ molecules• Diatomic means “two atoms”

– 2 halogen atoms _____ a valence electron from each atom, both atoms have 8 valence electrons

Covalent Bonds

• Multiple Covalent Bonds– N has 5 v.e. • if they shared a ____ of electrons, each one would have

only 6 v.e. • if they shared 2 pairs of electrons, each ____ would

have only 7 v.e.• Share 3 pairs of electrons, each atom has 8 v.e.

– Each ___ of shared electrons is represented by a long dash in the ________ formula

Covalent Bond

• Multiple Covalent Bond– ______ bond- when 2 atoms share 3 pairs of

electrons– _______ bond- when 2 atoms share 2 pairs of

electrons– ______ bond- when 2 atoms share 1 pair of

electrons

Unequal Sharing of Electrons• In general, elements on the ____ of the periodic

table have a greater attraction for electrons than elements on the ____ have (except for noble gases)

• In general, elements at the ___ of a group have a greater attraction for electrons than elements at the bottom of a group have

• Fluorine (far right, top of group): has _______ attraction for electrons and is the most reactive nonmetal

Unequal Sharing of Electrons• Polar Covalent Bonds– Electrons may _____ be shared equally– Polar covalent bond: a covalent bond in which

electrons are not shared equally (polar- “opposite in character, ______, or direction”

– When atoms form a polar covalent bond, the atom with the greater attraction for electrons has a partial negative charge. The other atom has a partial ______ charge (δ- and δ+ are used to show which atom has which charge)

Unequal Sharing of Electrons

• Polar Covalent Bond– In a hydrogen chloride molecule, the shared

electrons spend ____ time near the chlorine atom than near the ________ atom

Unequal Sharing of Electrons

• Polar and Nonpolar Molecules– The type of atoms in a _____ and its shape are

factors that determine whether a molecule is _____ or nonpolar

Unequal Sharing of Electrons• Polar and Nonpolar Molecules– Carbon dioxide (CO2)• ______ bonds between each oxygen atom and the

central carbon atom• O has a ______ attraction for electrons than carbon

does, each double bond is polar• Molecule is linear: all 3 atoms are _____ up in a row

– The carbon-oxygen bonds are directly opposite each other; there is an equal pull on the electrons from opposite directions; the pulls cancel out and the molecule as a whole is nonpolar

Unequal Sharing of Electrons• Polar and Nonpolar Molecules– Water molecules (H2O)• 2 _____ bonds in a water molecule• The bonds are polar because O has a ______ attraction

for electrons than hydrogen does• The water molecules has a ____ shape rather than a

linear shape, the polar bonds do not cancel out• 2 H atoms are located on the same side of the

molecule, _______ the O atom• O partial negative charge• H partial _______ charge

Attraction Between Molecules

• Attractions between ____ molecules are stronger than attractions between ________ molecules