7.1 COMPOUND, ATOMS AND IONS Let’s review: look at these elements: Sodium (metal) Fluorine(non metal) Neon (noble gas)

STABILITY Both Na and F need to be stable ( have 8 electrons in their valence shell just like a noble gas ) such as Ne which is the nearest noble gas to them For ex: H will try to be like He Li will try to be like He Na will try to be like S will try to be like

BACK TO FLUORINE Fluorine needs just one more electron to become stable…. When it gains that one electron, it becomes an ion….

BACK TO SODIUM Na

A TREND Usually metals tend to lose electrons Non metals tend to gain electrons When metals and non-metals join in a chemical bond, it is called an ionic bond. Ex: Na and Cl

IONS When metals lose electrons they become positive ions When non-metals gain electrons they become negative ions What do these charges mean? Be O

LOOK AT THIS IONIC COMPOUND CaF 2

An ionic compound o A compound made up of (a metal + non-metal ) o One atom loses electrons and one atom gains electrons.

IONIC COMPOUNDS 1)Ionic solids exist as a solid in the form of an ionic lattice or crystals. The positive ions attract all of the negative ions, and vice versa. ex: table salt (NaCl): the 1:1 ratio of ions results in a simple square-shaped ionic crystal.

IONIC COMPOUNDS 2) Ionic compounds have high melting points 3) Ionic compounds are very hard and brittle 4) Ionic compounds conduct electricity when dissolved

IONIC COMPOUNDS ARE FORMED BETWEEN A METAL (+) AND A NON-METAL (-)

POLYATOMIC IONS 1)Polyatomic ions form ionic compounds with other ions. 2)Polyatomic ions are formed by covalent bonds, but bond ionically with other ions to form compounds. Polyatomic ions: PO 4 -3 OH - CO 3 -2 Ex: hydroxide ion (OH - ) will form an ionic bond with lithium (Li + ) to form lithium hydroxide (LiOH). Li + + OH -  LiOH (ionic)

Covalent compounds or molecular compounds o A compound made up of (a non-metal + non-metal ) o Atoms share electrons in the valence shells o No gaining or losing electrons. What kind of compound would be formed when oxygen and chlorine get together?

COVALENT COMPOUNDS Let’s look at O 2 Now both oxygens will have 8 electrons in their valence shells (be stable). All these covalent compounds are also referred to as molecules. CO 2, O 2, H 2 O

COVALENT COMPOUNDS 1) Covalent compounds have low melting points, boiling points. 2) Poor conductors of electricity Fig 9 page 181

SUMMARY Ionic Covalent Remember hydrogen is a non-metal !!!

7.2 We call the physical force that holds atoms together a chemical bond. The smallest particle of an element is called an __________. So the smallest particle of a nitrogen element is called _________

The smallest particle of a compound with ionic bonds is called ____________ Ex: the smallest particle of CaCl 2 is ___________ The smallest particle of a covalently bonded compound is called a ____________ Ex: The smallest particle of CO 2 is a ___________ That’s it !

HOMEWORK Page 174 1,2,9,11,12 Page , 11