C.W. BAKER HIGH SCHOOL

 

CORE IV Review Materials

Prepared by K. Schmidt/M. Foster

 

 

 

Chemical Bonds- the “glue” that holds atoms or ions together because of ELECTRON interactions!!!

 

I.                   Intramolecular Bonds-  between atoms or ions

 

a.     Ionic bond

-transfer of electrons (generally between a metal atom and a non-metallic atom)

-electronegativity difference of > 1.7

-results in the formation of ions which are then attracted to each other due to their opposite charges.

-example: sodium chloride 

 

b.     Covalent bond

- sharing of electrons (generally between two non-metallic atoms)

- electronegativity difference of < 1.7

- results in the formation of molecules

- example: water is a molecule made up of covalent bonds

- 3 kinds of covalent bonds

1.     polar covalent bonds – unequal distribution of charge (electroneg. diff. greater  than .2 but less than 1.7)

2.     nonpolar covalent bonds – equal distribution of charge (electroneg. difference almost zero)

3.     coordinate covalent bonds – both electrons come from the same atom. 

Examples: H3O+  and NH4+

           

c.     Metallic bond

- “sea of electrons”

-  between positive ions and mobile electrons

 

II.                Intermolecular Bonds – bonds or forces that hold molecules together.  Responsible for properties like hardness, melting point, boiling point.

 

a.     Hydrogen bonds (strongest)

- between Hydrogen and a highly electronegative element such as oxygen (example: hydrogen bonds hold water molecules together).

 

b.     dipole – dipole

- between polar molecules 

            

c.      Van der Waals (London Dispersion Forces)(weakest)

- temporary dipoles that are responsible for holding non-polar molecules together (example: Van der Waals forces are responsible for holding carbon dioxide molecules together.)

-  increase in strength with molecular size

 

 

 

WATER:                                                   

                                                                  

                                                                  

v   Polar Molecule

v   Bent (not symmetrical)

v   2 lone pairs of electrons.

v   Held together by hydrogen bonds

 

AMMONIA:                                             

                  

v   Polar Molecule

v   Pyramidal (not symmetrical) 

v   1 lone pair of electrons

v   Molecules held together by hydrogen bonds

 

METHANE:                                             

                                                                  

                                                                  

v   Nonpolar Molecule

v   Tetrahedral (SYMMETRICAL)

v   NO lone pairs of electrons

v   Held together by London forces

 

CARBON DIOXIDE:                              

                                                                  

                                                                  

v    Nonpolar Molecule

v    Linear (SYMMETRICAL)

v    NO lone pairs of electrons (C)

v   Held together by London forces

 

For an overview of the properties associated with the different substances formed from the different types of bonds, click here