ATOMS

Phet Simulation: Build an Atom

1. What particle determines what element you have?

2. What particle(s) can change without changing the identity of an element?

3. What particle determines whether or not an element is an ion?

Atoms: the building blocks of matter?

Image via ThinkGeeks

Never trust an Atom! They

make up everything!

An atom is the smallest unit of an element that is possible.

H H

OAll the matter around us is made of individual

atoms. Sometimes different atoms join together to form new substances.

Two Hydrogen Atoms will join an Oxygen atom and

form water (H2O).

In this sense atoms are the building blocks of matter but atoms are usually made up of three smaller particles and two of those particles are made up of even smaller particles. So

an atom is not a fundamental building block of matter.

Molecule: consists of individual atoms in fixed proportions.

Protons, Neutrons and Electrons

• Positively charged (+1).• Found in the nucleus.• Defines what an atom is.

• Neutral particle in an atom.• Found in the nucleus.• Required for stability.

• Negatively charged particle (-1).• Found outside the nucleus.• Main cause of Chemical Bonding.

Protons, Neutrons and Electrons

• Protons and Neutrons are roughly equal in mass but a neutron is ever so slightly bigger than a proton.

• A proton (and a neutron) are about 1800 times as massive as an electron.

A proton and electron would NEVER balance!

Protons, Neutrons and Electrons

• Protons and Neutrons are roughly equal in mass but a neutron is ever so slightly bigger than a proton.

• A proton (and a neutron) are about 1800 times as massive as an electron.

Protons, Neutrons and Electrons

• Protons and Neutrons are roughly equal in mass but a neutron is ever so slightly bigger than a proton.

• A proton (and a neutron) are about 1800 times as massive as an electron.

It would take 1800 Electrons to balance with 1 Proton or Neutron!

Model of a Helium Atom

Nucleus: Dense central region in an atom where neutrons and protons are found. Contains most of the mass of an atom.

A typical Helium atom • 2 Protons• 2 Neutrons• 2 Electrons

Image Captured From Phet Physics Simulation

26

FeIRON

55.85

The Periodic Table

Atomic Number

Average Atomic Mass

The number of protons in the

nucleus of the atom

The total number of protons AND neutrons in the atom’s nucleus

6

CCARBON

12.01

A neutral carbon atom has how many of each particle?

Protons:_______

Neutrons:______

Electrons:_____

6

The 6 on the top is the atomic number of carbon and that is also the number of protons any atom of carbon must have.

6

The 12.01 on the bottom is the average atomic mass and is also the number of protons and neutrons in average carbon atom. Six of those 12 must be protons because Carbon has an

atomic number of 6 so what is left over are neutrons.

6

An electrically neutral must have an overall charge of 0. This means the total number of electrons (-1 charge) must be

equal to the number of protons (+1 charge).

8

OOxygen

16

Protons:_______

Neutrons:______

Electrons:_____

8

+1 +1+1 +1 +1+1+1 +1

8

0 00 0 000 0

8

-1 -1-1 -1 -1-1-1 -1

+8

-8

10

NeNEON

20.18

Proton Number = Atomic Number.

Neutron Number: Atomic Mass (rounded) minus Atomic Number.

(or bottom minus top)

Electron Number = Proton Number (if Neutral)

Protons:_______

Neutrons:______

Electrons:_____

CONCEPT CHECK

Why do we only consider the number of neutrons and

protons when determining the average atomic mass of

an atom?

ANSWER: Electrons are much lighter than protons and neutrons so we can ignore them.

Data Table 1Element

NameElement Symbol

Atomic Number

Atomic Mass

Electron Number

Proton Number

Neutron Number

HydrogenOxygenNeonCarbonNitrogen

Element Name

Element Symbol

Atomic Number

Atomic Mass

Electron Number

Proton Number

Neutron Number

He6

1135

61

Build these atoms using the phet physics simulation.Neatly draw them using the same color scheme that the app uses.

Just How Small is an Atom? (vid)

• How many copper atoms lined up side by side would equal a line 1cm in length?

• Atoms will NEVER be seen optically since atoms are smaller than the wavelength of visible light.

• Are you sitting in your chairs?

neutron mass 1.674927211 x10-27kg proton mass 1.672621637 x10-27 kg

neutron-proton mass ratio 1.00137841918electron charge -1.602176487 x 10-19c Proton charge +1.602176487 x 10-19c

electron mass 9.1 x 10-31 kg

Scientific Notation!

“Atoms are so tiny that I inhale billions of trillions with each breath, nearly a trillion times more atoms than the total population of people since time zero! In each breath, I inhale billions of atoms exhaled by every person who ever lived, excepting newborn babies far away. But atoms I’ve recycled are now part of them. From a physics point of view, we’re all one . . .

There are about as many atoms of air in your lungs at any moment as there are breathfuls of air in the atmosphere of the whole world. (There are about 10^22 atoms in a liter of air at atmospheric pressure, and about 10^22 liters of air in the atmosphere.) When you exhale a single breath of air, in about 6 years that breath becomes evenly mixed in the atmosphere. Then, every person in the world that inhales a breath of air gets, on average, one of the many atoms you exhaled in that single breath! And this occurs for each breath you exhale! Considering the many thousands of breaths that people exhale, at any moment you have hordes of atoms in your lungs that were once in the lungs of every person who ever lived. We are literally breathing one another.”

(Hewitt, Conceptual Physics, 8th. Ed –pg 180)