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 SODIUMNa

A TRENDUsually 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 CaF2

An ionic compound

o A compound made up of (a metal + non-metal )

o One atom loses electrons and one atom gains electrons.

IONIC COMPOUNDS1) 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 COMPOUNDS2) 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 IONS1) 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: PO4 -3 OH- CO3-2

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 shellso No gaining or losing electrons.

What kind of compound would be formed when oxygen and chlorine get together?

COVALENT COMPOUNDS Let’s look at O2

Now both oxygens will have 8 electrons in their valence shells (be stable) . All these covalent compounds are also referred to as molecules.

CO2, O2, H2O

COVALENT COMPOUNDS1) 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 !!!

7.2We 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 CaCl2 is ___________

The smallest particle of a covalently bonded compound is called a ____________

Ex: The smallest particle of CO2 is a ___________

That’s it !

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