Catalyst – March 6+2, 2012Remember, this is on your own paper

1. What is ONE difference between an element and a compound?

2. What is ONE difference between ionic and covalent compounds?(Use your book if you need

to!)

Today’s Agenda

Catalyst Welcome to Unit 3!!! Notes

Lewis Dot Structures Stable Ions and Oxidation Numbers Octet Rule

Exit Question

HW: Workbook Pages 83-85

Today’s Objectives

SWBAT describe a chemical bond.

SWBAT draw Lewis Dot Structures for atoms and ions.

SWBAT use the octet rule to predict the stable ion an atom will form in a chemical bond.

Unit 3: Chemical Hook-Ups

In this unit, you will be learning about how atoms hook-up, or bond. The unit will include… Lewis Dot Structures: Octet Rule,

Stable Ions, Number of Bonds Ionic Compounds vs. Covalent

Compounds Formulas and Names for

Compounds Chemistry.com profile and Speed

Dating

NOTES:Intro to Bonding

What is a compound?

Key Point #1: A compound results from interaction between valence electrons of different atoms.

Bonding

Key Point #2: There are two main ways that valence electrons interact between atoms to create chemical bonds:

By completely transferring them to another element Ionic Bond

By sharing electrons with another element Covalent Bond

Chemical Bond Spotlight: NaCl (table salt)

2 different elements: Sodium (Na) Chlorine (Cl)

1 compound: Sodium chloride

(NaCl)

Na Cl

NaCl

NOTES:LEWIS DOT

STRUCTURES!

Valence Electrons

Valence electrons are the electrons in the outermost energy level

NUCLEUS

ALL TOGETHER, SODIUM HAS 11 ELECTRONS.

SODIUM HAS 1 VALENCE ELECTRON

P=11 N=12

Don’t Forget! Valence ElectronsElectrons in the outermost level or shell of the atom are the ones that determine the chemical reactivity of an element Outer s and p electrons These electrons are involved in bonding

Lewis Dot Structures

Key Point #3: Lewis Dot Structures only show the number of valence electrons in an atom.

Valence electrons are the only electrons involved in bonding

Valence electrons are the most important electrons

Drawing Lewis Dot Structures

1. Write element symbol.2. Determine number of

valence electrons.3. Place single dot on right side

and add single dots counterclockwise.

EXAMPLES COMING UP…

LDS Example 1: Sodium (Na)

1. Write element symbol.2. Determine number of

valence electrons.3. Place single dot on right

side and add single dots counterclockwise.

LDS Example 2: Neon (Ne)

1. Write element symbol.2. Determine number of

valence electrons.3. Place single dot on right

side and add single dots counterclockwise.

You try!

1. Boron2. Oxygen3. Lithium

Lewis Dot Sructures

What do the Lewis

Dot Structures

have in common?!?

!?

I have a couple QUESTIONS…

1. What kind of charge does an electron have?

(-1)

2. What kind of charge does an entire atom have?

Neutral (positives = negatives)

First thing you need to know about ionic bonds….

Key Point #4: An ion is an atom that has gained or lost an electron. Cation = positive ion (+)Anion = negative ion (-) +

-

Types of ions

Cation – a positive ion (+) “t” looks like (+)

Anion – a negative ion (-) “n” or onion for negative

Formation of Negative Ions (ANIONS) Imagine that electrons are

pieces of poop Is poop is flying into your

yard (an atom’s energy levels) a positive or negative thing?

So…if poop lands in your yard, are you more positive or more negative?

So…NEGATIVE ions are formed when an atom GAINS one or more electrons!

-

Formation of Positive Ions (CATIONS) Imagine that electrons are

pieces of poop Is poop in your yard (an

atom’s energy levels) a positive or negative thing?

So…if you get rid of the poop in your yard, are you more positive or more negative?

+

So…POSITIVE ions are formed when an atom LOSES one or more electrons!

Practice Questions

1. If an atom gains an electron it will have a ___________ charge.

2. If an atom loses an electron it will have a ___________ charge.

3. If chlorine gains 3 electrons it will have a _______ charge.

NEGATIVE

POSITIVE

3-

Ions!

Cl loses 4 Electrons

What is the stable ion?

Ions!

Cobalt gains2 electrons

What is the stable ion?

Ions!

Si3- What happened…

gain or lose…how many?

Ions

Si3- Silicon gains 3

electronsHow many total

electrons does Si have now?

Practice Problems – Write all down!

Write down the stable ion that will form for the following:

1. Sr gains 5 electrons 2. Phosphorous loses 1 electron

Then, answer how many electrons TOTAL will they have now?

Practice Problems – Write all down!

How many TOTAL electrons do the following ions have?

1. Cl2+

2. Li2-

3. Xe3+

4. O1-

5. Zn5-

Octet Rule

What is different about the valence shells of the elements on the Left and those on the Right?

The noble gases have full valence shells, the other atoms do not…

Octet Rule – Elements are

most stable when they have the

electron configuration of a

noble gas (Key Point next…)

Key Point #5: The octet rule says that atoms are most stable when they have a full valence shell (2 or 8 valence electrons).

1.Atoms can gain, lose, or share electrons to become stable (happy)

2.Atoms with 5 or more valence electrons will GAIN electrons to become stable (happy)

3.Atoms with 3 or less valence electrons will LOSE electrons to be stable (happy)

Octet Rule

Octet Rule - Examples

How many electrons will the following atoms gain or lose to become stable (happy)? How many TOTAL electrons will the atom then have? What is the STABLE ION?

1. F2. Se3. N4. Ca

Octet Rule – Examples

Element # e- Gained/L

ost

Total electron

s

Stable Ion

FormedBromine

Selenium

Nitrogen

Calcium

Need extra practice? Try these… How many electrons will the

following atoms gain or lose to become stable (happy)? How many TOTAL electrons will the atom then have? What is the STABLE ION?

1. P2. Kr3. Ca4. I5. K

Worksheet for Class or HW

Half Shee – eet!Take care of your

bidness and complete it tonight!

Exit Question

1. Anion = _______ charge, Cation = _______ charge

2. What is the STABLE ION that will form for the following elements? Say how positive or negative it will be.

Te3. Draw the LDS for the following elements

Magnesium

HW: Workbook Pages 83-85Unit 2 Test Corrections due

tomorrow!