7.2 – 7.3

7.2 – 7.3

NAT GEO CAVEShttp://www.youtube.com/watch?v=wgUFb_l4DLE

IONIC BONDSAlthough they are composed of ions, the

compounds are electrically neutral.Held together by the opposing charges of the ions,

because opposites attract!

Exampley time w/ Sodium & Chlorine

Na ClIf I just had

1 less e-, I would

totally have an OCTET.

If I just had 1 MORE e-, I

would totally have an OCTET.

REMEMBER!!!:1. They are both electrically neutral:

they don’t have a positive electric charge or negative electric charge.

2. They have more electrons than the picture shows.

Lewis diagrams only show the valence electrons.

Really, Na has 11 TOTAL e- while Cl has 17 TOTAL e-.

Exampley time w/ Sodium & Chlorine

Na Cl“It would be a

shame if someone just stole this here electron while I

was looking away...”

“Don’t mind if I

do, Sodium. Yoink.”

Exampley time w/ Sodium & Chloride

Cl

(-)

Na(+) Na

(+) ClNa

(0)

Exampley time w/ Sodium Chloride

ClNa

CHARACTERISTICS OF IONIC BONDSMost are *CRYSTALLINE SOLIDS at room

temperature*(i.e. they look like crystals and are solids)

When these are molten or dissolved in water, they conduct electricity very well.

These are, unfortunately not as strong

as metallic bonds.

FORMULA UNITSWhen we have a CHEMICAL FORMULA, the

number in front of an element or compound is called a FORMULA UNIT.

These are always whole numbers that are at least 1.

EXAMPLE: NaCl CHEMICAL FORMULA

forSodium Chloride

FORMULA UNITSforEach are 1

Ca(SO4)A Calcium Ion [Ca2+] and a Sulfate Ion [SO4

2-] make the ionic crystalline solid known as GYPSUM. These are some of the largest crystals in the world.

METALLIC BONDSMetals are arranged in compact and orderly patterns.These patterns look sort of like ionic bonds, but are

different.Instead of alternating ions, there are only metal cations

surrounded by a sea of “disloyal” electrons.The electron-cation bond is what holds together metals.It allows for great electrical conductivity, ductility, and

malleability.

STRESS ON METAL & IONIC BONDSA force applied to a metal crystal can cause the

cations to move past one another quite easily. Metal has some give.

A force applied to an ionic crystal can cause the ions to repel from one another. This causes the crystal to shatter.

HOW IT’S MADEhttp://www.youtube.com/watch?v=5R6Zvp3DEh0