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PPT – What does the atom really look like Do the electrons really orbit like the planets PowerPoint presentation | free to download - id: 22efa2-NzkzZ

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The Modern Quantum Description of the Atom

What does the atom really look like? Do the

electrons really orbit like the planets?

No. The negative charge the electrons carry

looks smeared outor like a cloud.

Another possible formation (note this is ONE

electron)

Other possible configurations (or symmetries)

These symmetries are responsible for the symmetry

in the bonding of solids!

Summary Atomic models

Greek Jellium Planetary Bohr (Quantum) Modern

Quantum

Scientific Notation

How do we write 1,000,000,000,000,000,000 in a

more compact form?

1,000,000,000,000,000,000

There are 18 zeros

We write this as 1 x 1018

How do we write 1,200,000,000,000,000,000?

Again there are 18 spots after the first number,

but we have to account for the 2.

Answer 1.2 x 1018

What is (1.82 x 1012) x (3.87 x 109)?

Step 1 group the numbers as follows (1.82 x

3.87) x (1012 x 109)

Step 2 multiply these 7.04

Step 3 add the exponents of the 10s 21

Step 4 Write the result 7.04 x 1021

What is (2.4 x 1020) / (1.6 x 1011)?

Step 1 (Group) (2.4/1.6) x (1020 / 1011)

Step 2 (Divide numbers) 1.5

Step 3 SUBTRACT exponents 9

Step 4 Write in scientific notation

1.5 x 109

What is 0.0000000000005 in scientific notation?

There are 13 digits. Thus we can write this as

5.0 x 10-13

What is (3.0 x 1012) x (2.0 x 10-4)?

6.0 x 108

What is (6.0 x 104) / (3.0 x 10-3)?

2.0 x 107

And now to use scientific notation

Charges Revisited

1 It comes it two types positive and

negative. 2 Charge is conserved. 3 Like

charges repel opposites attract. 4 It only

comes in discrete amounts (the amount that comes

with an electron).

Materials

Conductors materials where the electrons are

free to move through the material. Examples

include metals (like wires), salt water, etc.

Insulators Electron are NOT free to move through

the material. Examples include rubber, plastic,

wood, coatings on electrical cords, etc.

Conductors

Describe the forces between the two charges.

Since unlike charges attract, the electrostatic

force will try to pull them together.

How will the charges MOVE if the material is an

insulator?

They will NOT movethe electrons cant move in an

insulating material.

How will the charges move if the material is a

conductor?

They will move towards one another.

Describe the force between two negative charges

placed in a conducting material.

Like charges repel so the two charges will repel

one another.

How will the charges MOVE?

They will move away from one another.

Where will the charges end up?

WHY do the charges end up in this configuration??

They want to maximize the distance between them.

Now suppose that we have a metal ball with two

electrons in it. Where do the electrons go??

They should end up somewhere on the outer

perimeterthis will maximize the distance between

them.

Now suppose that we add a third electronwhere

will the three of them end up?

They will end up equidistant from each other, but

at the same time maximizing the distance from one

another.

What if there are FOUR charges?

Again, the charges will configure themselves to

maximize the distance from each of the other

charges. The results in them being an

equidistance apart.

What if there are 1 x 1015 free electrons in a

conductorwhere do they end up?

They end up spread out evenly on the SURFACE of

the conducting material!!