CHEMICALbonding

The formation of ionic compounds Conductivity: physical property of metals, ability of electrons to move freely throughout a material Few compounds are able to conduct electricity in the solid state BUT some conduct electricity when dissolved in water These compounds are called electrolytes Example: Sodium chloride (table salt); potassium iodide; calcium oxide Non-electrolytes do not conduct electricity in water Example: carbon dioxide, methane, silicon dioxide

WHY? The other name for electrolytes is IONIC COMPOUND Ionic compounds consist: METAL + NON-METAL = IONIC COMPOUND Atoms can gain or lose electrons in their outer layer to become more stable They want to have a similar outer shell to their nearest noble gas

example Draw the Bohr Diagram for the following elements: Sodium Fluorine Neon

Making ions Atoms follow the octet rule: each main group element wants to have eight electrons in its outer shell Atoms gain or lose electrons to get to 8 in the outer shell Ion: atom (or group of atoms) that has gained or lost one or more electrons Anion: an atom that carries a negative charge because it has more electrons than protons Cation: an atom that carries a positive charge because it has more protons than electrons

Valence electrons: electrons that are found in the outer shell (level) of the atom Metals tend to lose electrons and become cations Non-metals (except noble gases) tend to gain electrons and become anions

Examples Draw the ions for: Sodium (Na1+) Fluorine (F1-) Neon (Ne)

Ionic BONDING Occurs with a metal and non-metal Example: Sodium Chloride

COVALENT BONDING

PRACTICE LiF SrO Na2O

Most of the chemicals we encounter are molecular compounds, including: Acetylsalicylic acid, or Aspirin sugar water

Soft Drinks Sugar C12H22O11 Carbon Dioxide CO2 Water H2O

Living Organisms Make thousands of different kinds of molecular compounds Sugars, fats, and proteins are all molecular compounds Some of them are very large, containing thousands of atoms in a single molecule

- more electronegative goes first compounds Covalent - two non-metals - sharing of electrons - more electronegative goes first - form molecules Ionic - metal and nonmetal - transfer of electrons - cations and anions - form formula units

Molecular Compounds The majority of all known compounds are molecular Molecules consist of two or more non-metal atoms joined by a covalent bond A COVALENT BOND forms when atoms share electrons The chemical formula gives the exact numbers of atoms in each molecule Diatomic molecules consist of only two atoms of either the same or different elements

when two NONMETALS come in contact they will share electrons rather than transferring them, ex. O and O

covalent bond forms as a result of sharing of electrons very strong, stronger than ionic bond atoms that are covalently bonded form molecules when two atoms form a covalent bond the sharing of electrons allows each to satisfy the octet rule

Lewis Structures of Molecules shared electrons are shows as a dash pairs of valence electrons surrounding each atom and not involved in bonding are called lone pairs Ex. O2

ex. I2, N2, CO2, H20

Ionic Bond vs Covalent Bond An Ionic bond is the simultaneous strong attraction of positive ions and negative ions A covalent bond results from the sharing of outer electrons between non-metal atoms