CHEMICAL BONDING COVALENT BONDS IONIC BONDS METALLIC BONDS

Reflection (pg 62) What is a metallic bond? Compare/contrast it to ionic/covalent bond

Metallic Bonds How atoms are held together in the solid. Metals hold onto there valence electrons very weakly. Think of them as positive ions floating in a sea of electrons.

Sea of Electrons Electrons are free to move through the solid. Metals conduct electricity.

Characteristic of Metallic Bonds High electrical and thermal conductivity Malleable, ductile, high luster. Great amount of heat needed to break these bonds.

IONIC BONDING When an atom of a nonmetal takes one or more electrons from an atom of a metal so both atoms end up with eight valence electrons

IONIC BONDING IS THE COMPOUND AN IONIC COMPOUND?METAL NONMETAL SUBSCRIPTS

IONIC BOND FORMATION

IONIC BONDING ION – any atom with more or less electrons that it is supposed to have* *Remember that the number of electrons is supposed to be equal to the number of Protons if the atom has a neutral charge

IONIC BONDING Metals will tend to lose electrons and become POSITIVE CATIONS Normal sodium atom loses one electron to become sodium ion

Na +1 is called a sodium ion The +1 symbol means it has lost one electron IONIC BONDING

Nonmetals will tend to gain electrons and become NEGATIVE ANIONS Normal chlorine atom gains an electron to become a chloride ion

Cl -1 is called a chloride ion The -1 symbol means it has gained one electron IONIC BONDING

Properties of Ionic Compounds Hard, brittle solids. Strongest bond. Most dissolve in water Conduct electricity when dissolved in water. High melting/ boiling points- because of strong forces between ions.

Crystalline structure The POSITIVE CATIONS stick to the NEGATIVE ANIONS, like a magnet.

COVALENT BOND FORMATION When one nonmetal shares one or more electrons with an atom of another nonmetal so both atoms end up with eight valence electrons

COVALENT BONDING IS THE COMPOUND A COVALENT COMPOUND?NONMETAL NONMETAL YES since it is made of only nonmetal elements

Polar Bonds When two different atoms are connected, the atoms may not be shared equally. This is a polar covalent bond. pages.uoregon.edu

Nonpolar Bonds When the atoms in a bond are the same, the electrons are shared equally. This is a nonpolar covalent bond. 800mainstreet.com

Characteristics of Covalent Bonds Represented by Lewis structures Strong bond but weaker than Ionic bonds Low melting points & boiling points Most do not dissolve in water Do not conduct electricity. Usually in a gas state at room temperature

Covalent bonds Monatomic: contains one atom Diatomic: contains two atoms BrINClHOF Bromine (Br 2 ), Iodine (I 2 ), Nitrogen (N 2 ), Chlorine (Cl 2 ), Hydrogen (H 2 ), Oxygen (O 2 ), Fluorine (F 2 ) You must have these memorized!!!! Polyatomic: contains more than one atom.

Octet Rule Octet rule: atoms tend to gain, lose, or share electrons until they are surrounded by 8 valence electrons (4 electron pairs). Exceptions: Hydrogen forms bonds in which it is surrounded by only two electrons. Boron tends to form bonds in which it is surrounded by 6 electrons. Main group elements in period 3 and up can form bonds with expanded valance shells.

Lewis structure rules 1.Write the element symbol. Around this draw dots—one for each valence electron. 2. The dots sould be spread over four sides. Dots are not paired until all sides have at least one dot. 3. It does not matter on which side dots are placed. Example- Hydrogen can be drawn in four ways:

Lewis structure rules 4. The number of valence electrons is equal to the group number for groups 1 and 2. In groups 13 to 18, subtract 10 and that is the number of valence electrons.

Multiple bonds in Lewis Structures Molecules containing carbon (C), nitrogen (N), and oxygen (O) may form multiple bonds. The need for multiple bonds becomes obvious if there are not enough valence electrons to complete octets by adding unshared electron pairs.

Double bonds Produced by sharing two pairs of electrons between two atoms.

Triple Bonds Produced by sharing three pairs of electrons between two atoms.

MOLECULAR SHAPES OF COVALENT COMPOUNDS

VSepR tHEORY

What Vsepr means Since electrons do not like each other, because of their negative charges, they orient themselves as far apart as possible, from each other. This leads to molecules having specific shapes.

Things to remember Atoms bond to form an Octet (8 outer electrons/full outer energy level) Do NOT forget all electron pairs, including unshared electron pairs!!!

Linear The central atom is represented by A and the atoms bonded to the central atom are B. The molecule AB 2 is linear Bond Angle = 180° EXAMPLE: BeF 2

Trigonal Planar The molecule AB 3 makes an equilateral triangle. Bond Angle = 120° EXAMPLE: GaF 3

Tetrahedral The molecule AB 4 makes the shape of a tetrahedral (kind of looks like a pyramid). Bond Angle = 109.5° EXAMPLE: CH 4

Covalent bonding Fluorine has seven valence electrons F

Covalent bonding Fluorine has seven valence electrons A second atom also has seven FF

Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons FF

Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons FF

Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons FF

Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons FF

Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons FF

Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons l Both end with full orbitals FF

Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons l Both end with full orbitals FF 8 Valence electrons

Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons l Both end with full orbitals FF 8 Valence electrons

Single Covalent Bond A sharing of two valence electrons. Only nonmetals and Hydrogen. Different from an ionic bond because they actually form molecules. Two specific atoms are joined. In an ionic solid you can’t tell which atom the electrons moved from or to.

How to show how they formed It’s like a jigsaw puzzle. I have to tell you what the final formula is. You put the pieces together to end up with the right formula. For example- show how water is formed with covalent bonds.

Water H O Each hydrogen has 1 valence electron Each hydrogen wants 1 more The oxygen has 6 valence electrons The oxygen wants 2 more They share to make each other happy

Water Put the pieces together The first hydrogen is happy The oxygen still wants one more H O

Water The second hydrogen attaches Every atom has full energy levels H O H

Multiple Bonds Sometimes atoms share more than one pair of valence electrons. A double bond is when atoms share two pair (4) of electrons. A triple bond is when atoms share three pair (6) of electrons.

Carbon dioxide CO 2 - Carbon is central atom ( I have to tell you) Carbon has 4 valence electrons Wants 4 more Oxygen has 6 valence electrons Wants 2 more O C

Carbon dioxide Attaching 1 oxygen leaves the oxygen 1 short and the carbon 3 short O C

Carbon dioxide l Attaching the second oxygen leaves both oxygen 1 short and the carbon 2 short O C O

Carbon dioxide l The only solution is to share more O C O

Carbon dioxide l The only solution is to share more O C O

Carbon dioxide l The only solution is to share more O CO

Carbon dioxide l The only solution is to share more O CO

Carbon dioxide l The only solution is to share more O CO

Carbon dioxide l The only solution is to share more O CO

Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO

Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO 8 valence electrons

Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO 8 valence electrons

Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO 8 valence electrons

How to draw them Add up all the valence electrons. Count up the total number of electrons to make all atoms happy. Subtract. Divide by 2 Tells you how many bonds - draw them. Fill in the rest of the valence electrons to fill atoms up.

Examples NH 3 N - has 5 valence electrons wants 8 H - has 1 valence electrons wants 2 NH 3 has 5+3(1) = 8 NH 3 wants 8+3(2) = 14 (14-8)/2= 3 bonds 4 atoms with 3 bonds N H

NHH H Examples Draw in the bonds All 8 electrons are accounted for Everything is full

Examples HCN C is central atom N - has 5 valence electrons wants 8 C - has 4 valence electrons wants 8 H - has 1 valence electrons wants 2 HCN has = 10 HCN wants = 18 (18-10)/2= 4 bonds 3 atoms with 4 bonds -will require multiple bonds - not to H

HCN Put in single bonds Need 2 more bonds Must go between C and N NHC

HCN l Put in single bonds l Need 2 more bonds l Must go between C and N l Uses 8 electrons - 2 more to add NHC

HCN l Put in single bonds l Need 2 more bonds l Must go between C and N l Uses 8 electrons - 2 more to add l Must go on N to fill octet NHC