Chemical Bonding Ionic, Covalent, and Metallic bonding

Chemical Bonds When atoms chemically combine, they create a chemical bond. A chemical bond is an attractive force that holds atoms or ions together to form a molecule by transferring or sharing electrons.

In order to earn “stability”, each atom tries to have 8 e - in its outer most energy level. YOU MUST ALWAYS REMEMBER THE NUMBER 8 STABILITY- OCTET RULE

1. Ionic Bonds The three types of bonds: An ionic bond forms between a metal (cation) and a non-metal (anion). Electrons are transferred between atoms in an ionic bond.

Example animation for Chemical bonding: 7.sci.phys.matter.chembonds/

Properties of Ionic Compounds Structure Crystalline solids Melting & Boiling Points Generally high Electrical Conductivity Excellent conductors, molten and aqueous Solubility in water Generally soluble

Ionic Bonds are held by this force: ELECTROMAGNETIC FORCE: Ions come together due to electrostatic attraction (opposite charges attract) Cl - Example: Na + The net charge on the compound must equal zero Ions are charged atoms. Remember, if an atom loses an –e it becomes a + ion (cation), if it gains an –e it becomes a – ion (anion).

2. Covalent Bond Covalent bonding is between more than one nonmetal. Electrons are SHARED. Covalent bond = molecular compound A molecule is the basic unit of a molecular compound.

Example animation for Chemical bonding: 7.sci.phys.matter.chembonds/

Diatomic Elements include: 1. Hydrogen H 2 5. Chlorine Cl 2 2. Nitrogen N 2 6. Bromine Br 2 3. Oxygen O 2 7. Iodine I 2 4. Fluorine F 2 HH Shared electrons OO Diatomic elements are elements who are always found in pairs when they are alone. You MUST memorize all 7 of them. Horses Need Oats For Clear Brown I’s

1. Have much lower boiling and melting points than ionic compounds. 2. Can exist as solids, liquids, or gases. 3. Are usually softer substances than ionic compounds. 4. Are usually poor conductors of heat and electricity. Properties of Covalent Bond

 Occurs when two atoms equally share a pair of electrons.  The diatomic elements are examples of molecules containing a nonpolar covalent bond. Nonpolar Covalent Bonds OO

Occurs when two atoms do not equally share a pair of electrons. Occurs when two atoms do not equally share a pair of electrons. As a result of the unequal sharing of an electron pair, the molecule has one end which is partially negative ( δ-) and one end which is partially positive ( δ+). As a result of the unequal sharing of an electron pair, the molecule has one end which is partially negative ( δ-) and one end which is partially positive ( δ+). The negative end of one polar molecule will be attracted to the positive end of another polar molecule. The negative end of one polar molecule will be attracted to the positive end of another polar molecule. Polar Covalent Bonds

3. The Metallic Bond The bond between Metal and Metal is called metallic bond. Metal atoms have a tendency to lose their valence electrons n nn n n n n n n n n n n n n n n n -e -e -e -e -e -e -e -e -e - e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e -e - e -e -e -e -e -e -e When metals form a “metallic crystal” they simply dump their valence –e into a “sea of electrons” to be shared by all the nuclei of all the atoms in the metal

Animation for Chemical bonding: 7.sci.phys.matter.chembonds/

Properties of Metals Metals are good conductors of heat and electricity Metals are malleable Metals are ductile Metals have high tensile strength Metals have luster

Bonds and Properties The type of bond formed between atoms of different elements determine many of the properties of the compound formed. IONIC BONDS are the strongest bonds because of electromagnetic force. This bond accounts for: high melting pointhardness brittlenessshape (crystals) COVALENT BONDS are the weakest bonds. low melting pointsdull finish METALLIC BONDS ductilitymalleability conductivityluster

Predicting Types of Bonds By type of element: Metal + Nonmetal Ionic Bond Nonmetal + NonmetalCovalent Bond Metal + MetalMetallic Bond By location on PT Left + RightIonic Bond Right + RightCovalent Bond Left + LeftMetallic Bond By lose/gain –e Lose + GainIonic Bond Share + ShareCovalent Bond Lose + LoseMetallic Bond All of this is important