Chapter 5, Section 3 Covalent Bonds

Ionic Bonds Covalent Bonds (Molecular Bonds) Occur between a metal and a non-metal Electrons are given (cations) or taken (anions) Occur when two non-metals share electrons in a chemical bond Atoms can even bond with other atoms of the same element (ex. Flourine molecule) Molecule = a neutral group of atoms joined by covalent bonds Table talk: Explain how two flourine atoms could bond together in a covalent bond based on their electron arrangement.

“Sharing is caring and caring is covalent.”

How many bonds? The # of covalent bonds a non-metal atom can form = the # of electrons needed to make a total of 8 (ex. Ammonia) Double and triple bonds can form when atoms share more than one pair of electrons

Molecular compounds Compounds composed of molecules Atoms in these compounds are covalently bonded Lower melting/boiling points Do not conduct electricity when melted or dissolved in water Table Talk: In relation to ionic compounds, why do you suppose molecular compounds have lower melting or boiling points? (hint: think about their bonds) Table Talk: In relation to ionic compounds, why do you suppose molecular compounds do not conduct electricity? (hint: think about their bonds) DOCUMENT CAMERA ACTIVITY: Refer to text p. 195, “Math --Analyzing Data” to compare molecular and ionic compounds

Unequal Sharing of Electrons The atoms of some elements in a covalent bond pull more strongly than others Unequal sharing of electrons causes the bonded atoms to have slight electrical charges Polar bond = a covalent bond in which the electrons are shared unequally Nonpolar bond = a covalent bond in which the electrons are shared equally See BrainPop “Chemical Bonds”

Attractions among molecules Because polar molecules have negatively and positively charged ends, they tend to attract other molecules On the other hand, non-polar molecules do not attract each other See covalent bonding video: http://www.youtube.com/watch?v=UR4eG60jjQQ end