Chapter 8 Chemical Bonding

Section 1: Electrons & Chemical Bonding Vocabulary Chemical Bonding Chemical Bond Valence electron

Combining Atoms All substances made of one or more atoms of the 100+ elements Chemical bonding is the joining of 2 or more atoms to form a new substance

Combining Atoms Chemical bond is the interaction that keeps molecules together. Models are used since chemical bonding is complex and microscopic.

Electron Number & Organization Electrons are key to bonding!! Electrons are organized into energy levels. Only electrons in outer energy level form bonds

Electron Number & Organization Outer energy electrons are called valence electrons Remember == elements are grouped based upon similar properties on PTOE All atom within a group have same # of valence electrons

To Bond or Not to Bond # of valence electrons determine if and how an atom forms bonds All atoms want to fill their outer most energy level Either by sharing electrons (covalent) Or by giving/taking electrons (ionic)

Section 2: Ionic Bonds

Vocabulary Ionic bond Ion Crystal lattice

Forming Ionic Bonds Ionic bonds when valence electrons transfer from 1 atom to another atom

Forming Ionic Bonds Normally the number of protons and electrons equal each other No overall charge to the atom 10+ and 10- = no charge Ions are charged atoms Number of electrons change Protons will never change

Forming Positive Ions Atoms that lose electrons form a positive ion 3 protons (+) 2electrons (-) ------------------ 1+ charge

Forming Positive Ions Most metals have outer energy level with a few valence electrons Most metals form positive ions

Forming Positive Ions Metals tend to lose valence electrons Takes energy to remove electrons Groups 1 & 2 of PTOE require less energy to remove their valence electron You’ll only find ions of these metals in nature

Forming Negative Ions Atoms that gain electrons are negative ions 2 protons (+) 3 electrons (-) ------------------ 1- charge

Forming Negative Ions Atoms of nonmetals have nearly full valence Oxygen has 6 electrons in its valence level Needs only 2 electrons to be full full = stable Energy is released when electrons are gained

Forming Ionic Compounds “ ide” suffix used for names of compounds formed from negative compound number of electrons lost = number of electrons gained by non-metal New compound is neutral in charge

Forming Ionic Compounds Ionic Compound is a chemical change All chemical changes = new properties New properties are different from original

Forming Ionic Compounds Ionic compounds form a crystal lattice Repeating 3-Dimensional pattern Other properties Brittle solids High melting points Very high boiling points Highly soluble in water

Covalent and Metallic Bonds Section 3: Covalent and Metallic Bonds

Vocabulary Covalent bond Molecule Metallic bond

Covalent Bonds Chemical bond formed when atoms share electrons Formed between two non-metals atoms

Covalent Bonds Covalent bonds are formed from molecules Molecules = 2 or more atoms joined together in a definite ratio

Covalent Bonds Electron-dot diagrams Representation/model of valence electrons Used to predict number of bonds an atom might form

Covalent Bonds Electron-dot diagrams uses octet rule Octet = 8 8 valence electrons = stability

Covalent Compounds & Molecules Atom = smallest particle that an element can be divided and still be that element Molecule = smallest particle that a covalently bonded compound can be divided and still be that same compound

Covalent Compounds & Molecules Molecules are at least 2 covalently bonded atoms Some elements are only found in molecules in nature Called diatomic elements Oxygen Nitrogen All halogens

Covalent Compounds & Molecules More complex molecules formed from multiple atoms Carbon is common atom to form complex molecules 1 Carbon can make up to 4 bonds

Metallic Bonds Metallic bond forms between positive metal ion and electrons in metal bonds, atoms are close together Outermost energy levels overlap Valence electrons can move throughout metal

Properties of Metal Due to metallic bonds, metals have unique properties Conduct electric current Ductile  drawn into wires Malleable  able to be pounded/shaped Bends without breaking

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