Ionic Bonds

Chemical Bond A chemical bond is a force that holds atoms or ions together in a compound Bonds form so that ions can become STABLE

Ionic Bonds in Detail When atoms form an ionic bond, their electrons are transferred (lost or gained) to the other atom You need a : Metal and a nonmetal Positive Ion and a Negative Ion Cation and an Anion The overall # of protons & electrons of the combined atoms remains equal and unchanged therefore, the compound is neutral!

Crystals Crystals are solids whose particles are arranged in a lattice structure Ionic compounds have a crystalline structure.

Properties of Ionic Compounds Solids High melting/boiling points Good conductors of electric current when melted Often shatter when struck w/ hammer due to very strong bonds

Number of Valence electrons Gain / Lose electrons to become stable Group number Number of Valence electrons Gain / Lose electrons to become stable Ion Charge/ Oxidation Number Group 1 Metals 1 Lose 1 1+ Group 2 Metals 2 Loses 2 2+ Group 13 3 Lose 3 3+ Group 14 4 Lose or Gain 4 4+ or 4- Group 15 5 Gain 3 3- Group 16 Nonmetals 6 valence electrons Gains 2 2- Group 17 Nonmetals 7 valence electrons Gains 1 1-

There are 3 kinds of chemical bonds! Ionic Bonds– force of attraction b/w opposite charges of ions (the transfer of electrons) Covalent Bonds – force of attraction between negative charges of ions (the SHARING of electrons) Metallic Bonds – force of attraction between positive charges of ions (a “SEA OF ELECTRONS”

Octet Rule In forming compounds, atoms tend to achieve electron configurations of a noble gas They either gain to 8 or lose to 0 (so that the outer energy level “drops” and their inner level is stable with 8)

Chemical Formula Chemical Formula – tells what elements a compound contains and the exact number of the atoms of each element Ex: H2O – 2 hydrogen and 1 oxygen The 2 is a subscript (written below) it tells us how many atoms of that element are in that compound * If there is no subscript, it is assumed there is only 1 unit

Drawing Ionic Bonds Practice For each set of elements, draw an ionic bond using Lewis Structures or Bohr Diagrams (You must draw 3 Lewis and 3 Bohr diagrams!): K + Cl Ca + O Li + Br (this one MUST be a Lewis Structure) Mg + Cl Na + S Li + F

Covalent Bonds

Covalent Bonds in Detail The neutral particle that forms as a result of electron sharing is called a molecule. Single covalent bond – made up of 2 shared electrons

Double/Triple bonds Double bond- forms when 2 pairs of electrons are shared Triple bond- forms when 3 pairs of electrons are shared

Covalent Bond Examples

Polar and Nonpolar Molecules Polar molecule – has a slightly positive end & a slightly negative end. Ex: H2O Nonpolar molecule – all electrons are shared equally in bonds. Ex: CCl4

Ionic Covalent Structure Network of ions (crystal lattice) molecules Valence electrons transferred shared Electrical conductivity Good (when melted or dissolved) poor State at room temp solid Solid/liquid/gas Melt/boiling pt. Generally high Generally low