Warm Up:Dimensional Analysis Practice

The relative mass of an electron is 0.000586 amu.

a. Write in scientific notation

b.If a proton has a relative mass of 1.007276 amu, how many electrons could fit on a proton?

c. The actual mass of an electron is 9.109 x 10-31kg. Convert to mg

Chapter 3: Atoms, the Building

Blocks of Matter

Atomic Theory has Evolved!Why has the atomic theory changed through the years?

Qualitative vs. Quantitative data

Law of Conservation of Mass

Mass is neither created nor destroyed during an ordinary chemical reaction or physical change.

Candle Lab:

C25H52 + O2 + E CO2 + H2O + C + E

Draw a picture and explain why it happens?

1. Tear up a piece of paper. Rub the balloon against your clean, dry (product free) hair. Hold the balloon next to the paper. Make observations.

2. Rub the balloon against your hair. Hold the balloon close to running water. Make observations.

3. Explain to the best of your abilities what is happening.

Pioneers of the Atomic Theory

Chapter 3

Observant people have been looking at matter and pondering why different phenomenon occur for hundreds of years.

Early Philosophers

Didn’t agree!!

Dead Dude #1- Democritus

Ancient philosopher- 460BC

Matter is made of indivisible particles.

Atomos means “that which cannot be further broken down”

ShortcomingsIt is a conceptual definition, not based on science.

Doesn’t talk about subatomic particles.

Dead Dude#2- DaltonExplained the Laws

John Dalton (early 1800s)

Atom is a solid, indestructible mass (like a billiard ball)

All Atomic Theory builds on Dalton’s Law

1. All matter is made of tiny particles called atoms.

2. All atoms of a given element are identical in size, mass and properties Atoms of each element are different.

3. Atoms cannot be subdivided, created or destroyed.

4. Compounds consist of atoms of different elements combined together. Compounds have constant composition (fixed ratio of atoms).

5 Chemical reactions involve the rearrangement of those atoms.

Through observation and experimentation we have found that some are true, others are not!

1. All matter is made of tiny particles called atoms.

2. All atoms of a given element are identical in size, mass and properties

3. Atoms of each element are different.4. Atoms cannot be subdivided, created of

destroyed. 5. Compounds consist of atoms of different

elements combined together. Compounds have constant composition (fixed ratio of atoms).

6. Chemical reactions involve the rearrangement of those atoms.

Dead Dude #3J.J Thomson- 1850

A ball of positive mass containing a number of electrons that are embedded.

Getting the idea that there are protons and electrons (nucleus).

Shortcomings

Doesn’t explain the existence of electrons outside the nucleus or their importance in bonding.

No neutrons- can’t explain radioactivity or the existence of isotopes.

What did experiments with the cathode ray tubes teach us?

http://www.youtube.com/watch?v=O9Goyscbazk&safety_mode=true&persist_safety_mode=1&safe=active

Late 1800’s

Discovery of and experiments using the cathode ray tube led to our understanding of the electron.

Millikan Oil Drop ExperimentMillikan Oil Drop Experiment

We learned what the actual charge of an electron is– pretty cool!

Henri Becquerel- 1897

Researched newly discovered X-rays (Phosphorescence).

Accidently discovered that uranium emits radiation that could be measured using photographic plates.

Discovered Radioactivity- electrically charged particles.

The Dr’s Curie- 1898Discovered new elements- Polonium and Radium.

Very unstable elements that give off energy.

This led to an under- standing of Alpha, Beta and Gamma particles.

Dead Dude #4 Rutherford Model- 1905

Mass of the atom is concentrated in the center of a positively charged region called the nucleus.

The Planetary Model

Gold Foil Experiment- Draw this and write about the experiment.

Ask Ben…

Gold Foil Experiment

ShortcomingsDoesn’t place the electrons.

Doesn’t include neutrons.

Warm Up- Leave enough space to finish the atomic theory ppt

(2 more slides)

The actual mass of a proton is 1.673 X 10-27 kg. a. What is the mass of 6300 protons?b. Convert your answer to decigrams.c. Convert your answer to megagrams.

Believed that electrons traveled in precise orbits around the nucleus of an atom

Bohr Model-1920

Describes mathematically the wave properties of electrons and other very small particles

The nucleus is at the center of the atom and the electrons are in the electron cloud.

Schrodinger Quantum Mechanical Model.

Reading the Periodic Table Cell

PracticeElement Symbol Protons Neutrons Electrons

Magnesium

23

Ca

8 8

Chlorine

How did you do?Element Symbol Protons Neutrons Electrons

Magnesium Mg 12 24-12 =12 12

Vanadium V 23 51-23 = 28 23

Calcium Ca 20 41-20 = 21 20

Oxygen O 8 8 8

Chlorine Cl 17 35-17 = 18 17

Build an Atom Activity…Get a computer… type in

Build an atom phet

Write everything in bold print

Answer every question…

You have about 35 minutes to get this done!

Draw the Bohr Model for the following

atoms….Na N Cl

The octet rule says that atoms will be more stable when they have a full outer shell… usually 8 valence electrons.

IonsIons are atoms that gain or lose electrons to obtain a full outer shell (a complete octet).

Cations- lose electrons

Anions - gain electrons

IonsThe number of protons does not change in an ionThe number of neutrons does not change in an ion.So, both the atomic number and the atomic mass remain the

same.

How do I calculate the average atomic mass of an element?

Look at just about any element on the periodic table. Do you notice that most of the atomic masses listed are not whole numbers.

Hmmmmm……..Can we have a part of a

proton or neutron?

I don’t think so!

What we are looking at is the average atomic mass of the isotopes.

Some Kr atoms are 83amuothers are 84amu

So… how do they get that number?The calculation:

1. Write the percent abundance (given)

2. Change to relative abundance

3. Multiply relative abundance by mass

4. Add’em up!

Easy as pie!

Let’s talk donuts!

Veggium Lab

Let’s Practice!- Please copy the table into CB

Element #Protons #Neutrons #Electrons

Oxygen

Calcium

Aluminum

Tungsten

Nickel

Let’s Practice!- Output p.23Please copy the table into CB

Element #Protons #Neutrons #Electrons

Oxygen 8 16 – 8 = 8 8

Calcium 20 20 20

Aluminum 13 27-13=14 13

Tungsten 74 184-74=110 74

Nickel 28 59-28=31 28