“Ionic and Metallic Bonding”

Valence Electrons are… Responsible for the chemical properties of atoms Valence electrons - The s and p electrons in the outermost energy level

Keeping Track of Electrons Atoms in the same column have the same... outer electron configuration valence electrons. The number of valence electrons = the group number for representative elements

X Electron Dot Diagrams Write the symbol Put one dot for each valence electron (8 max) They don’t pair up until they have to (Hund’s rule) X

Nitrogen Electron Dot diagram Nitrogen has 5 valence electrons Write the symbol. N Then add 1 electron at a time to each side. Now they must pair up.

The Octet Rule… In forming compounds, atoms tend to achieve a noble gas configuration 8 electrons in the outer level is stable Each noble gas (except He) has 8 e- in the outer level

Formation of Cations Metals lose electrons to attain a noble gas configuration. They make positive ions (cations) Na 1s22s22p63s1 1 v.e. Na1+ 1s22s22p6 8 v.e.

Electron Dots For Cations Metals have few valence electrons (usually 3 or less) Ca

Electron Dots For Cations Metals will lose the valence electrons Ca

Electron Dots For Cations We have now formed a positive ion This is named the calcium ion. Ca2+ NO DOTS are now shown for the cation.

Electron Configurations: Anions Nonmetals gain electrons to attain noble gas configuration. Make negative ions (anions) S = 1s22s22p63s23p4 = 6 v.e. S2- = 1s22s22p63s23p6 = noble gas configuration.

Electron Dots For Anions Nonmetals will have 5, 6 or 7 v.e. They will gain electrons P3- P phosphide ion

Ionic Bonding Anions and cations are held together by opposite charges. Ionic compounds are called salts. Simplest ratio of elements in an ionic compound is called the formula unit.

Ionic Bonding The bond is formed through the transfer of electrons. Electrons are transferred to achieve noble gas configuration. Bond is electrostatic

Ionic Bonding Na Cl The metal (Na) tends to lose its one electron from the outer level. The nonmetal (Cl) needs to gain one to fill its outer level, and will accept the electron that sodium is going to lose.

Ionic Bonding Na+ Cl - Note: Remember that NO DOTS are now shown for the cation!

Ionic Bonding Let’s do an example by combining calcium and phosphorus: Ca P All the electrons must be accounted for, and each atom will have a noble gas configuration (which is stable).

Ionic Bonding Ca P

Ionic Bonding Ca2+ P

Ionic Bonding Ca2+ P Ca

Ionic Bonding Ca2+ P 3- Ca

Ionic Bonding Ca2+ P 3- Ca P

Ionic Bonding Ca2+ P 3- Ca2+ P

Ionic Bonding Ca Ca2+ P 3- Ca2+ P

Ionic Bonding Ca Ca2+ P 3- Ca2+ P

Ionic Bonding Ca2+ Ca2+ P 3- Ca2+ P 3-

Ionic Bonding = Ca3P2 Formula Unit This is a chemical formula, which shows the kinds and numbers of atoms in the smallest representative particle of the substance.

Properties of Ionic Compounds Crystalline solids - a regular repeating arrangement of ions in the solid Ions are strongly bonded together. Structure is rigid. High melting points

Conducting electricity means allowing charges to move. Do they Conduct? Conducting electricity means allowing charges to move. In a solid, the ions are locked in place & they do not conduct.

Do they Conduct? When melted, the ions can move around. Melted ionic compounds conduct. NaCl: melts at about 800 ºC Dissolved in water, they also conduct

Naming Ionic Compounds Oxidation Number Ionic Names Ionic Formulas Chemical Bonds Naming Ionic Compounds Oxidation Number Ionic Names Ionic Formulas

A. Oxidation Number The charge on an ion. Indicates the # of e- gained/lost to become stable. 1+ 2+ 3+ 4+ 3- 2- 1-

B. Ionic Names Write the names of both elements, cation first. Change the anion’s ending to -ide. Write the names of polyatomic ions. For ions with variable oxidation #’s, write the ox. # in parentheses using Roman numerals. Overall charge = 0.

B. Ionic Names NaBr Na2CO3 sodium bromide FeCl3 sodium carbonate iron(III) chloride

C. Ionic Formulas Write each ion. Put the cation first. Overall charge must equal zero. If charges cancel, just write the symbols. If not, crisscross the charges to find subscripts. Use parentheses when more than one polyatomic ion is needed. Roman numerals indicate the oxidation #.

C. Ionic Formulas potassium chloride magnesium nitrate K+ Cl-  KCl copper(II) chloride K+ Cl-  KCl Mg2+ NO3-  Mg(NO3)2 Cu2+ Cl-  CuCl2

C. Ionic Formulas calcium oxide aluminum chlorate Ca2+ O2-  CaO iron(III) oxide Ca2+ O2-  CaO Al3+ ClO3-  Al(ClO3)3 Fe3+ O2-  Fe2O3