CHEMISTRY October 19 th, 2011. Welcome Back! October 19 th, 2011 Brainteaser: –Let’s reflect on last quarter’s performance: 1.What are some things you

CHEMISTRY

October 19th, 2011

Welcome Back! October 19th, 2011

• Brainteaser:– Let’s reflect on last quarter’s performance:

1. What are some things you thought you did well for this class?

2. What are some things you think you could improve for this quarter?

3. What is your overall goal for this quarter (i.e. what do you want to accomplish this quarter and how are you going to do it?)

Agenda

• Brainteaser

• Unit 5: Ionic Bonding Notes

• Homework– Ionic Bonding Practice Worksheet

Unit 4: Chemical Bonding

• Bonding– Differences in chemical behavior are due to

differences in the types of bonds– Bond: forces that hold atoms together in

molecules or ionic compounds.

Chemical Bonding• Types of bonds and types of substances

– Ionic

– Covalent

– Metallic• The type of bond between atoms is partially

responsible for the properties of the substance.

Chemical Bonding

• Bonding– Involves the valence electrons or outermost shell (or

highest shell) electrons– For group A elements – the group number tells how

many valence electrons• For example:

– K, Ca, C, B, N, F, Ne

– Lewis Dot Structures show the valence electrons around an atom and for most molecules and compounds a complete octet for the elements is needed.

• For example: N, Al, H2O

Lewis Dot Structures

• These symbols are called Lewis symbols

• We generally place the electrons on four sides of a square around the element symbol.

Drawing Lewis Dot Structure

• Place DOTS around the SYMBOL clockwise pairing up dots on the second time around– For example:

• Magnesium (Mg) and Oxygen (O) MgO

Mg

O

Ionic BondingIonic Bonding

Ions and Ionic Compounds

• Ions are formed by adding or subtracting electrons from a neutral atom or molecule.

• Cation: positively charged ions (remove e-)

• Anions: negatively charged ions (add e-)

Two Types of Ions• Monatomic ions

– Single atom ions• O 2-

• Na+

• Al3+

• Polyatomic ions– More than one atom ions

• NH4 +

• OH –

• SO4 2-

• Electron Counts of Stable Ions– Ions tend to have the same number of

electrons as the nearest noble gas.• Transition metals are not as predictable, but +2

and +3 are common.

Predicting Charges of Ions

Main Group ElementsMain Group Elements

Note periodicity of charges

Transition ElementsTransition Elements• Not periodic; +2 and +3 common

• Oxoanions generally have the same charge as the simple anion of the same nonmetal.

Charges and Formulas of Oxoanions

Charges and Formulas of Oxoanions

Related to position in the periodic table; note exceptions for B, C, N

Polyatomic Ions

tend to reflectthe charge of the base element

Ionic Bonds form when…

• A cation (metal) bonds with an anion (nonmetal)

• A salt is formed:– For example: Sodium: Na “metal” bonded to

Chlorine: Cl “nonmetal”– For example: Magnesium: Mg “metal” bonded

to Chlorine: Cl “nonmetal”

Ionic Bonding:Ionic Bonding:The Formation of Sodium ChlorideThe Formation of Sodium Chloride

Sodium has 1 valence electron

Cl: 1s22s22p63s23p5

Na: 1s22s22p63s1

Chlorine has 7 valence electrons

An electron transferred gives each an octet

Cl- 1s22s22p63s23p6

Na+ 1s22s22p6

This transfer forms ions, each with an octet:

Ionic Bonding:Ionic Bonding:The Formation of Sodium ChlorideThe Formation of Sodium Chloride

Cl- Na+

The resulting ions come together due to electrostatic attraction (opposites attract):

The net charge on the compound must equal zero

Na+


Cl- Na+


The net charge on the compound must equal zero


Lewis Dot Drawing• Ionic bond

• Example– Lewis Dot

diagram

• A positively charged ion is attracted to a negatively charged ion.

• A transfer of electrons• Metal and a Non-Metal

• NaCl



• NaCl



• NaCl

Na Cl Na ClNa ClNa ClNa Na

Practice

• Draw the Lewis dot structures for the following compounds:– CaO

– BaCl2– Na2S

Writing Formulas for Ionic Compounds

• Crisscross Method

• Example:

Ca and F

• Write the element symbols for the cation and anion, with the cation on the left and the anion on the right.

• Write each ion’s charge as a superscript.

• Crisscross the two charges moving them downward diagonally from one superscript to the other subscript.

Practice

• Write the correct formula for the ionic compounds composed of the following pairs of ions using the crisscross method:– Potassium and iodide– Magnesium and chloride– Aluminum and bromide– Cesium and nitride– Barium and sulfide– Iron (II) and fluoride

CHEMISTRY

October 20th, 2011

Warm Up

• Write the correct formula for these ionic compounds:– Aluminum oxide– Barium nitride– Iron (III) oxide– Magnesium carbide

Agenda

• Brainteaser

• Grade Homework: Practice W/S

• Unit 5 Notes:– Naming Ionic Compounds– Properties of Ionic Compounds

• Partner Bonding Activity

• Homework:– Naming Ionic bonds W/S

Naming Ionic Compounds

• Step 1: – Cation is written first in the name; anion is written second in the

name• Name of cation is the same as the neutral atom element

(Na+ = Sodium)

• Step 2: – Anion is written by adding the suffix –ide to the root of the

element name (I- = iodide)• For example: NaCl = Sodium Chloride, Al2O3 = Aluminum oxide

• Step 3: – Figure out if you need a Roman numeral in the name (transition

metals). • Figure out what the Roman numeral should be

– For example: Fe2O3

• Step Four: Check your work

PracticeNaming Ionic Compounds

• KF

• AlF3

• KCl

• Na3P

• Fe2O3

Properties of Ionic Bonding

• Definition:– In an ionic bond, a positively charged ion is

attracted to a negatively charged ion• Electrostatic Attraction


• Solid at room temperature• Electrical conductivity

– Conducts electricity when dissolved in water or in liquid (molten) form

– Dissociated ions can carry charge through the solution

• Hardness– Hard but brittle– Electrostatic repulsion

• Melting points and Boiling points– High melting and boiling point– Forces of attraction between positive and negative ions

are strong


Quiz

• Write the chemical formula for these ionic compounds:– Sodium bromide– Potassium nitride– Beryllium phosphide

• Write the chemical names for these ionic compounds– SrCl2– MgI2

– Ba3N2

Documents

CHEMISTRY October 19 th, 2011. Welcome Back! October 19 th, 2011 Brainteaser: –Let’s reflect on last quarter’s performance: 1.What are some things you