Covalent BondsCovalent Bonds

Understanding how oil and Understanding how oil and water can be made to mix water can be made to mix

together.together.

What are covalent bonds?What are covalent bonds?► Covalent bonds occur Covalent bonds occur

when two or more when two or more atoms come together atoms come together and share an electrons.and share an electrons.

► The force that holds The force that holds atoms together in a atoms together in a covalent bond is the covalent bond is the attraction of each attraction of each atom’s nucleus for the atom’s nucleus for the shared pair of electrons.shared pair of electrons.

► Examples of molecules Examples of molecules with covalent bonds are with covalent bonds are NHNH33, F, F22, O, O22, N, N22, and CO, and CO22..

Multiple bondsMultiple bonds► Double and triple bonds are Double and triple bonds are

common in covalent atoms.common in covalent atoms.► A bond between two atoms A bond between two atoms

contains two electrons, and contains two electrons, and is represented by two dots is represented by two dots between two elements.between two elements.

► A double bond contains four A double bond contains four electrons and produces two electrons and produces two bonds.bonds.

► A triple bond contains six A triple bond contains six electrons and produces three electrons and produces three bonds.bonds.

► Oxygen (OOxygen (O22) has a double ) has a double bond, while (Nbond, while (N22) has a triple ) has a triple bond.bond.

Molecular compoundsMolecular compounds► Molecules come Molecules come

together to produce a together to produce a molecular compound.molecular compound.

► Compared to ionic Compared to ionic compounds molecular compounds molecular compounds have lower compounds have lower melting points and melting points and boiling points.boiling points.

► Molecular compounds Molecular compounds also do not conduct also do not conduct electricity when electricity when dissolved in water or dissolved in water or melted. (NaCl and water melted. (NaCl and water is an ionic combination is an ionic combination by comparison).by comparison).

Comparing molecular and ionic Comparing molecular and ionic bondsbonds

SubstanceSubstance FormulaFormula Melting Melting pointpoint

(Degree C)(Degree C)

boiling boiling

(Degree C)(Degree C)

MethaneMethane CHCH44 -184.4-184.4 -161.5-161.5

Rubbing Rubbing alcoholalcohol

CC33HH88OO -89.5-89.5 82.482.4

Zinc Zinc chloridechloride

ZnClZnCl22 290290 732732

Magnesium Magnesium chloridechloride

MgClMgCl22 714714 14121412

An unequal sharing of An unequal sharing of electronselectrons

► In molecular compounds In molecular compounds the electrons are not the electrons are not distributed equally distributed equally through the molecule.through the molecule.

► The result is a molecule The result is a molecule which has a slight charge which has a slight charge to it as a entire molecule.to it as a entire molecule.

► The need to possess all The need to possess all of the atoms is similar to of the atoms is similar to a game of tug of war, a game of tug of war, except the molecule is except the molecule is having this battle with having this battle with itself.itself.

Polar and nonpolar bonds.Polar and nonpolar bonds.►Polar covalent bonds occur Polar covalent bonds occur

when electrons are shared when electrons are shared unevenly which produces a unevenly which produces a positive and a negative end positive and a negative end of a molecules. (HF acid, of a molecules. (HF acid, and Hand H22O are examples.)O are examples.)

►Water is the universal Water is the universal solventsolvent

►Non polar covalent Non polar covalent molecules occur when molecules occur when electrons are shared equally electrons are shared equally by the atoms in a molecule. by the atoms in a molecule. (F(F22, and CO, and CO22 are examples) are examples)

Understanding how oil and Understanding how oil and water can mix.water can mix.

►Water contains polar bonds Water contains polar bonds and oil contains non polar and oil contains non polar bonds.bonds.

►Detergent is a large molecule Detergent is a large molecule which has a polar bond at one which has a polar bond at one end and a non polar bond at end and a non polar bond at the other.the other.

► The detergent acts like a glue The detergent acts like a glue which binds both water and which binds both water and oil to itself on opposite ends oil to itself on opposite ends in order to remove oil from a in order to remove oil from a substance while being substance while being suspended in a water solution. suspended in a water solution.