Chemical Bonds (general), Ionic, Covalent, & Metallic Bonds BONDING Chemical Bonds (general), Ionic, Covalent, & Metallic Bonds

Discuss with your elbow partners CHEMICAL BONDS: GENERAL What type of electron configuration (# valence electrons) do atoms need to be stable? What group of elements is naturally stable? What do elements do to become stable if they don’t have a full valence shell? What is a chemical bond? What is a compound? Discuss with your elbow partners

IONIC BONDS

1. What is an ionic bond? Atoms GAIN or LOSE electrons (which gives them positive or negative charges and makes them ions). Always between a METAL and NONMETAL

2. Properties of Ionic Compounds When ions bond together, they form ionic compounds. Ionic compounds are: Brittle Have high melting points (usually solids) Dissolve in water/conduct electricity

3. Example/additional notes F K

K F

K F

K F

K F

K F

K F

+ _ K F Cation Anion

K F _ + The ionic bond is the attraction between the positive K+ ion and the negative F- ion

K F _ Potassium Fluoride + NOW CALLED The ionic bond is the attraction between the positive K+ ion and the negative F- ion NOW CALLED Potassium Fluoride

http://www.youtube.com/watch?v=zpaHPXVR8WU

Review - Work with your elbow partner to complete the Review at the top of page 2.

Review Ionic bonds form between a METAL and a NONMETAL. Metals will LOSE electrons while nonmetals will GAIN electrons. This makes the metal have a + charge (CATION) and the nonmetal have a - charge (ANION). These opposite charges cause the atoms to be attracted to each other.

Review Group 1 will form ionic bonds with group 17. Group 2 will form ionic bonds with group 16. To name the new compound, name the metal first and change the nonmetal’s ending to -ide.

Element Atomic Symbol Total electrons # of Valence electrons Electron Dot Diagram (EDD) # of Electrons lost or gained Charge on Atom (oxidation #) Bromine Lithium Calcium Sulfur Chlorine Carbon and Silicon Explain why these won’t form ionic bonds.

Sodium + Chlorine Magnesium + Iodine Potassium + Iodine Sodium + Oxygen EDD   EDD for ions formed (include correct charge and # of atoms for each) Formula of new compound: Name of new compound: EDD for ions formed (include correct charge and # of atoms for each) EDD for ions formed (include correct charge and # of atoms for each) EDD for ions formed (include correct charge and # of atoms for each)

COVALENT BONDS

So what are covalent bonds?

In covalent bonding, atoms still want to achieve a full outer electron shell. (the octet rule).

But rather than losing or gaining electrons, In covalent bonding, atoms still want to achieve a full outer electron shell (the octet rule). But rather than losing or gaining electrons, atoms share an electron pair.

The shared electron pair is called a bonding pair. In covalent bonding, atoms still want to achieve a noble gas configuration (the octet rule). But rather than losing or gaining electrons, atoms now share an electron pair. The shared electron pair is called a bonding pair.

Covalent bonds occur between TWO nonmetals. In covalent bonding, atoms still want to achieve a noble gas configuration (the octet rule). But rather than losing or gaining electrons, atoms now share an electron pair. Covalent bonds occur between TWO nonmetals.

Chlorine forms a covalent bond with itself Cl2

How will two chlorine atoms react? Cl Cl

Cl Cl Each chlorine atom wants to gain one electron to achieve an octet

Cl Cl do to achieve an octet? What’s the solution – what can they Neither atom will give up an electron – What’s the solution – what can they do to achieve an octet?

Cl Cl

Cl Cl

Cl Cl

Cl Cl

Cl Cl octet

Cl Cl octet circle the electrons for each atom that completes their octets

Cl Cl The octet is achieved by each atom sharing the electron pair in the middle circle the electrons for each atom that completes their octets

Cl Cl The octet is achieved by each atom sharing the electron pair in the middle circle the electrons for each atom that completes their octets

Cl Cl This is the bonding pair circle the electrons for each atom that completes their octets

Cl Cl It is a single bonding pair circle the electrons for each atom that completes their octets

Cl Cl It is called a SINGLE BOND circle the electrons for each atom that completes their octets

Single bonds are abbreviated Cl Cl Single bonds are abbreviated with a dash circle the electrons for each atom that completes their octets

This is the chlorine molecule, Cl Cl This is the chlorine molecule, Cl2 circle the electrons for each atom that completes their octets

O2 Oxygen in the air is composed of two covalently bonded molecules

O How will two oxygen atoms bond?

O Each atom has two unpaired electrons

O

O

O

O

O

O

O both atoms want to gain two electrons.

O . both atoms want to gain two electrons.

O

O O

O O

O O

Both electron pairs are shared.

O O 6 valence electrons plus 2 shared electrons = full octet

O O 6 valence electrons plus 2 shared electrons = full octet

O O two bonding pairs, making a double bond

can be shown as two dashes. = The double bond can be shown as two dashes.

This is the oxygen molecule, = this is so cool! This is the oxygen molecule, O2

Video showing Na + Cl  NaCL (ionic Bond) 2H + O  H20 http://youtube.com/watch?v=yjge1WdCFPs Another video showing ionic and covalent bonds http://youtube.com/watch?v=QqjcCvzWwww

METALLIC BONDS

Metallic Bonding Metallic bonds = attraction between metal ions and delocalized electrons Electrons are far from the nucleus and free to travel around “sea of electrons” Valence shells of nearby atoms overlap Electrons can flow between atoms (electricity) when an atom’s electrons “leave” it becomes a positive ion which attracts nearby electrons Free electrons can slide over each other, nuclei follow  metals are malleable and ductile

Metallic Bonds: Mellow dogs with plenty of bones to go around These bonds are best imagined as a room full of puppies who have plenty of bones to go around and are not possessive of any one particular bone. This allows the electrons to move through the substance with little restriction. http://www.bsc2.ehb-schweiz2.ch/Chemie/Simulationen%20Chemie/Bindung/Bindung%20Hundeanalogie.htm (for other bond type analogies)