A QUICK BONDING REVIEW

Why do atoms want to bond? To achieve the octet rule OCTET RULE: atoms want to have 8 valence electrons in their outer most shell because it makes them stable

What is the difference between a bond and a compound? A bond is the link between two (or more) elements in a compound Na---Cl it involves valence electrons A compound is what two (or more) elements linked together is called NaCl

What are the different types of bonds and/or compounds? IONIC COVALENT METALLIC

IONIC BOND bond between a metal and a nonmetal involves transfer of electrons one atom gains electrons (anion); the other atom loses electrons (cation) attraction between oppositely charged ions holds ions together strongest bond the compound with an ionic bond is also called a FORMULA UNIT example: the bond between sodium & chlorine in NaCl

COVALENT BOND bond between two nonmetals there is “cooperation between valence electrons” or sharing of electrons neither atom loses e- easily; both attract e- by sharing e-, outer energy level is filled attraction between nucleus and shared e- holds atoms together strong bond, but weaker than ionic the compound with a covalent bond is also called a MOLECULE example: the bond between carbon & oxygen in CO 2

METALLIC BONDS between 2 metals positive nuclei of atoms surrounded by free-moving electrons all electrons attracted by all the nuclei at the same time

NAMING AND WRITING CHEMICAL FORMULAS

Naming Ionic Compounds Remember: between a metal & nonmetal fluorine  becomes fluoride sulfur  becomes sulfide oxygen  becomes oxide phosphorus  becomes phosphide nitrogen  becomes nitride iodine  becomes iodide

Example: LiBr Name metal: Name nonmetal: Add –IDE ending:

More Examples CaCl 2 Calcium chloride Notice that the subscripts do not matter in the name Rb 2 O Rubidium oxide

Naming Covalent Compounds Remember: between 2 nonmetals You need to use GREEK prefixes mono (1) hexa (6) di (2) hepta (7) tri (3)octa (8) tetra (4)nona (9) penta (5) deca (10)

Naming Covalent Compound con’t 1. 2.

Example: CCl 4 Using GREEK prefix, name 1 st nonmetal : Using GREEK prefix, name 2 nd nonmetal : CCl 4  (note: if mono is on the 1 st non-metal it should be omitted)

More Examples NO Nitrogen monoxide P 2 F 6 Diphosphorus hexafluoride

Writing Ionic Compounds Remember ionic charges! (also called oxidation numbers) Alkali metals (+1) Alkaline Earth metals (+2) Boron family (+3) Nitrogen family (-3) Oxygen family (-2) Halogens (-1) Remember to use your Periodic Table!

Writing Ionic Compounds con’t 1. 2.

Example: aluminum oxide Determine each element’s charge: aluminum oxygen Criss-cross the charges: (note: you may eliminate a subscript of 1)

More Examples Lithium oxide Barium bromide = Li 2 O =BaBr 2

Writing Covalent Compounds 1. 2.

Example: dioxygen pentabromide Use the GREEK prefixes to determine the subscripts: – dioxygen  – pentabromide  Dioxygen pentabromide 

More Examples Triiodine heptafluoride I3F7I3F7 Pentaphosphorus decaoxide P 5 O 10

What is a polyatomic ion? It is an ion (or has a charge) and is composed of more than one element covalently bonded Example: NO 3 –1 This is the nitrate ion  the whole thing has a charge of –1 and it is composed of 1 nitrogen atom and 3 oxygen atoms See list on page 173).

Naming Compounds… with polyatomic ions Remember that the subscripts do not matter in the name of IONIC compounds

Example: Ca(NO 3 ) 2 Name metal or positive polyatomic ion: Name nonmetal or negative polyatomic ion: Ca(NO 3 ) 2 

More Examples NH 4 Br ammonium bromide Mg(OH) 2 magnesium hydroxide

Writing Compounds… with polyatomic ions Use (parenthesis) if polyatomic ion has a subscript

Example: barium perchlorate Determine each charge: Criss-cross:

More Examples Potassium Cyanide K +1 CN -1 KCN Magnesium phosphate Mg +2 (PO 4 ) -3 Mg 3 (PO 4 ) 2

Other thoughts… Write the formula for beryllium sulfide Beryllium: Be +2 Sulfide: S -2 you would think… Beryllium sulfide  Be 2 S 2 But cancel subscripts to make….BeS