Essential Question:

How do you determine the formula for an ionic compound?

Do Now – March 16th, 2015

• Complete half sheet

Agenda – March 10th, 2015

• 5 Do Now• 3 Agenda & Reminders– Academic Assistance this Saturday!

• 15min Notes– Follow your worksheet!

• 10min Guided Practice• 0-15min Independent Practice– Backside is additional EMI 402 practice

• Answers: B, H, B, J D

• 5min Exit Ticket

What ion will As form?

• 5 valence electrons– Wants a total of? – Lose 5?• Nahhhh, no thanks.

– Gain 3?• Now that’s easier!

8

As As3-

What ion will Sr form?

• 2 valence electrons– Wants a total of? – Gain 6?• Nahhhh, no thanks.

– Lose 2?• Now that’s easier!

8

Sr Sr2+

Ionic Bonds and Compounds

• Ionic bonds are bonds between ions!

• Ionic compounds are 2 or more different ions held together by their opposite charges.

• Ionic compounds are between metals and nonmetals

• Note: The bond that forms is not a “bridge” of some sort. The atoms bond or stick together because of their opposite charges.

Becoming Neutral

• Ionic compounds are formed from charged particles (excess of negative or positive charge)

• But they come together in ratios so that they always form a NEUTRAL compound

• The excess positive and excess negative MUST cancel each other out

What this looks like…

P=11N=11

P=17N=18

Sodium (Na) Chlorine (Cl)

1+ 1-

What this looks like…

Sodium (Na) Chlorine (Cl)

P=11N=11

1+

P=17N=18

1-

Goal of ionic bonding: balance out the charges!

Na1+ Cl1-

Thanks for the electron. Want to balance my

charge now?

What if the Charges don’t match?

• Use the smallest whole number ratio so that the charges will cancel each other out.

• If you have a 3+ ion bonding with a 1- ion, you will need THREE of the 1- ions in order to cancel out the charge of the 3+ ion

Al3+Cl-

Cl-Cl- AlCl3

What if it isn’t 1 to 1…

P=12N=11

P=17N=18

Magnesium (Mg) Chlorine (Cl)

1+1-

P=17N=18

2+

1-

What if it isn’t 1 to 1?

Mg Cl2+ 1-

Thanks for the electron. Want to balance my

charge now?

What if it isn’t 1 to 1?

Mg Cl2+ 1-

1 EXTRA + over here!

Cl 1-

Writing formulas for compounds

MgCl

Cl

1 Mg2 Cl

Mg1 Cl2

subscripts (“below – writing”)

Writing formulas for compounds

Mg1 Cl2

Scientists are lazy/efficient!!!Make the “1” invisible.

Writing formulas for compounds

Mg Cl2

Scientists are lazy/efficient!!!Make the “1” invisible.Clean it up….

MgCl

Cl MgCl2

Li F1+ 1-

All canceled!!!Formula: LiF

#2…

Li O1+ 2-

1 EXTRA - over here!Li 1+Formula: Li2O

Toot that thang up, chemists. Make it charge!

• Write the element symbols and their charges.

Mg2+ Cl-

Once you pop, pop lock it. Now those ions livin’ large.

Pop the charge over to the other element and lock it there.

Pop, lock, and drop it…

1. Drop the numbers to subscripts.

2. Drop the +/-3. Drop the 1’s to be

invisible

Magnesium and chlorine combine to make the ionic compound MgCl2.

For a

lum

inum

(Al)

and

chlo

rine

(Cl)

Ionic Formulas, summary

• The subscript will match the charge of the opposite ion

• EXCEPT when they can be reduced– Magnesium (2+) and sulfur (2-)– Mg2S2 REDUCE– MgS

Helpful hints• First determine if it is ionic, covalent, or an

acid• If it is ionic, write the charges above each

name– Magnesium Phosphate

• If it is an acid, determine what the anion is by working backwards and write its charge– Nitric acid (anion = nitrate, 1- charge)

2+ 3-

Complete the rest of the worksheet and CHECK IN with me after you complete each section. When finished, you may

start your homework