Introduction to chemistry

Using the Periodic Table Atomic Number  Symbol – “Shorthand” for the element – Note 2nd letter is always lowercase  Atomic Mass Number – Total AVERAGE mass of Protons + Neutrons + El

Chemistry Unit Notes

Basic Vocabulary

 Mass: Amount of matter in an object

objects due to mass and gravity

contained in a given volume

More Vocabulary

properties of matter:

to form a new substance

Sub-Atomic Particles

Part of

nucleus

.0006 amu

(too little to count)

Periodic Table

Using the Periodic Table

 Atomic Number

 Symbol

– “Shorthand” for the element – Note 2nd letter is always lowercase

 Atomic Mass Number

– Total AVERAGE mass of Protons + Neutrons + Electrons

17

Cl

35.5

Electron Energy Levels

 Electrons are arranged in “Shells” around nucleus in

 Ex Carbon has 6 total electrons so…

Two electrons on first energy level

17 electrons orbiting nucleus

Notice: electrons follow energy level rules from previous slide.

(Round Atomic Mass)

Atomic Mass – Fractions?

– 0.5 protons? 0.5 neutrons?  No

and neutrons in nature

More Practice

neutrons and electrons for each element shown and draw…

(same protons) but can have diff # of neutrons

– Carbon (14) and carbon (12) exist in

nature

charge (+ or -)

(protons don’t change)

– Ex Count the number of electrons below…

Carbon ion (-1 charge)

Valence Electrons

in how atoms will BOND with each other

Electron Dot Diagrams

 a diagram that represents the # of valence

electrons in an atom of an element.

 The amount of electrons is displayed by dots

around the symbol of the element

 Ex.

 http://www.fordhamprep.org/gcurran/sho/sho/le ssons/lesson38.htm

Types of Chemical Bonds

 Ionic- Two elements bond by transferring electrons to create ions that attract together (+ is attracted to - after an electron is transferred)

 Covalent- Two elements bond by sharing electrons (strongest bond type)

 Metallic- Two metals bond and form a “common electron cloud” This is a cluster of shared electrons (weakest bond type)

Examples of Bonding

http://www.youtube.com/watch?v=xTx_DWboEVs http://www.youtube.com/watch?v=1wpDicW_MQQ http://www.youtube.com/watch?v=QqjcCvzWwww http://lc.brooklyn.cuny.edu/smarttutor/core3_22/Bonds.html

Predicting Bonds

Oxidation Numbers

 Oxidation numbers are assigned to each element

 They represent a predicted “charge” of an atom/ion when it bonds with another element.

 (tells us if the atom would prefer give or take electrons, and how many).

 They help us to predict what compounds will form when two elements get together.

 Oxidation numbers are labeled like this:

 Na 1+

 O

2-How to Use Oxidation Numbers

Oxidation Number indicates the number of electrons lost, gained or shared when

bonding with other atoms.

Ex Na wants to lose an electron If an electron is lost, it

becomes a +1 charge

SO: oxidation number for Na = 1+

Ex Cl wants to gain an electron If an electron is gained, it becomes a -1 charge

SO: oxidation number for Cl =

1-Oxidation Numbers

has elements with the same oxidation

number

 Label the oxidation numbers on your periodic table at the top of each column as shown here:

1+ 2+ 3+ 4 (+/-) 3- 2- 1- 0

Rules for using oxidation numbers to create compounds

1 Positive ions can only bond with negative ions and vice

versa

2 The sum of the oxidation numbers of the atoms in a

compound must be zero (the key is to stay balanced)

3 If the oxidation numbers are not equal to zero, then you

must add additional elements until they balance at zero.

4 When writing a formula the symbol of the Positive (+)

element is followed by the symbol of the negative (-) element

Examples of Forming Compounds

Ex Na (+1) + Cl (-1) = NaCl

Are these oxidation numbers already equal to zero?

If so, you don’t need to add any extra elements to combine them into a compound, so the answer is simply NaCl

How many +1 would you need to balance the -2 to zero?

Since you need 2 atoms of the 1+ to balance the 2- to zero the resulting compound would be H2O

In other words: to combine H with O, you MUST have 2 H to balance the oxidation numbers to zero 2+ and 2- = ZERO

This one is tricky…we are not even close to balancing + and - to zero.

Because of this we must have more than one Al and more than one S in our final equation.

By using 2 Aluminums instead of just1 we would have 6+

Chemical vs Physical Change

without changing the identity of the

substance.

– Ex Solid, Liquid, Gas (Phase change)

substance becomes a new and different

substance

– Ex Fire

Chemical Reactions

physical and chemical properties of the

original substance change as new

substances with different physical and

chemical properties are formed

Chemical Reaction Basics

Evidence of Chemical Change

 EPOCH is an acronym that stands for evidence that a chemical reaction has occurred.

 – Effervescence (bubbles and/or gives off gas)

 – Precipitate (solid crystals form)

 – Odor (change of smell is detected)

 – Color change

 – Heat (reaction either heats up or cools down)

 Does sighting evidence of a chemical reaction mean that a chemical reaction has undoubtedly taken place?

Types of Reactions

Romance Chemistry :)Synthesis- Marriage/Dating

A + B = ABDecomposition- Divorce/Breakup

AB= A + BSingle-Replacement- Dance Cut In

A + BC = AC + BDouble-Replacement- Dancing couples switch partners

AB + CD = AC + BD

Cartoon Chemistry

This is an example of synthesis

Cartoon Chemistry

This is an example of a decomposition

Cartoon Chemistry

This is an example of a single replacement

Cartoon Chemistry

This is an example of a double replacement

Reaction Types Review…

the reaction types on your chemical

Conservation of Mass

chemical reaction

mass

Balancing Equations

 Rules:

– We can not add or subtract subscripts from either

side of the equation

– We can only add coefficients to the front of each

compound

 Ex 2H 2 + O 2 > 2H 2 O

H = 4 H = 4 O=2 O = 2

Before must match After See “Balancing Act” worksheet for more examples…

Solution Chemistry

but not chemically combined

dissolved into another

 Solute = Substance that gets dissolved (ex Kool-Aid powder)

 Solvent = Substance that does the dissolving (ex Water)

 Acid: Compound with a pH below 7 that tastes sour and is a

proton donor.

 Ex Citrus foods

 Base: Compound with a pH above 7 that tastes bitter and is a proton acceptor

 Ex Cleaning Products (soap)

Acids and Bases

- Solutions can be acidic or basic

- Acids and Bases have unique properties when dissolved in water

- Acids = sour taste

- Bases = bitter taste

with a solution, which helps to determine if a substance is

an acid or a base (pH paper, Litmus paper, cabbage juice)

mixed with water

– Ammonia

– Soap

– Bleach (chlorine)

Combining Acids and Bases

-Mixing acids and bases is a balancing act (like a teeter-totter)

Acid + Base = neutral (water and salt)

Combining Acids and Bases

EXAMPLE:

Acid + Base = neutral (water and salt)

H+ + OH-  HOH + Salt

Acid Base water

Measuring Acids and Bases

solution

Acids and Bases