Chemical bonding

3 Types of Chemical Bonds Ionic Covalent Metallic What can you describe about each of these bonds just by looking at the name?

CHEMICAL BOND The force of attraction that holds atoms together as a result of the rearrangement of electrons between them. Bonding is a way to gain stability. Involves valence electrons. Valence Electrons – the electrons in the outermost energy level of an atom This Lithium Atom has one valence electron

predict bonding preference? You can tell what type of bonding is in a substance by looking at whether the elements in it are metals or non-metals: Metals + Nonmetals → Ionic Bonds Nonmetal + Nonmetal → Covalent Bonds Metal + Metal → Metallic Bonds

Metals + Nonmetals → Ionic Bonds Nonmetal + Nonmetal → Covalent Bonds Metal + Metal → Metallic Bonds

CONSIDER EIGHT A HAPPY NUMBER FOR ATOMS! The Octet Rule Atoms will combine to form compounds in order to reach eight electrons in their outer energy level. Atoms with less than 4 valence electrons tend to lose electrons. Atoms with more than 4 valence electrons tend to gain electrons. Be aware that there are some exceptions! CONSIDER EIGHT A HAPPY NUMBER FOR ATOMS! Eight is GREAT! 

Oxidation Number The charge that an atom would have if it lost or gained electrons; ionic charge Can be helpful in determining which atoms will interact or bond with each other Example: 2+ Mg

Let’s try to predict charges…… Lewis Dot Structures Let’s try to predict charges…… Metal or Nonmetal?

Ionic bond Definition Example: Sodium Chloride (NaCl) Ionic bonding is an attraction between oppositely charged ions. Occurs after the gain/loss of electrons. Usually forms between atoms of metals and atoms of non-metals.

Metals + Nonmetals → Ionic Bonds This Photo by Unknown Author is licensed under CC BY-NC-ND

Covalent Bonds

Covalent Bonds O H A bond that forms when two atoms share an electron. Each pair of shared electrons creates a bond Usually occurs between atoms of non-metals + - O H - - - + - - - + - - - Water – H2O

Nonmetal + Nonmetal → Covalent Bonds

Covalent bond polarity

Covalent Bonds A covalent bond in which electrons are shared equally is called a nonpolar bond. A covalent bond in which electrons are shared unequally is called a polar bond.

Unequal Sharing (Polar Covalent Bond) The unequal sharing of electrons between two atoms that gives rise to negative and positive regions of electric charge Results from an atom’s electronegativity – the ability to attract electrons to itself + + + + Electron Cloud Bonded hydrogen atoms showing equal sharing of electrons Hydrogen and Chlorine bond with an unequal sharing of electrons Why do you think the two Hydrogen atoms share equally, but the Hydrogen and Chlorine do not?

Metallic Bond

how the electrons do not just stay with one ion Metallic Bond An attraction between a positive metal ion and the electrons surrounding it. Recall most metals have 1, 2, or, 3 valence electrons Many properties of metals, such as conductivity, ductility, and malleability, result from the freely moving electrons in the metal Al3+ - - - Notice how the electrons do not just stay with one ion - - - - - - - - - - -

Metallic Bonds Netal atoms share ALL of their valence electrons with ALL of the other metal atoms around them is called a metallic bond. The positive nuclei of metal atoms are surrounded by the free-moving valence electrons that are all attracted by the nuclei at the same time. This vast area of valence electrons is often described as a “sea” of electrons.

An alloy is a mixture made of two or more elements that has the properties of metal.