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Atoms

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Gracie Zamarron

on 6 September 2013

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Transcript of Atoms

Atoms
Atomic Structure and Atomic Theory
The smallest particle of an element
What is an atom?
The inside of an atom is comprised of the nucleus
What are the parts of the atom?
Atoms are often referred to as the building blocks of matter
Each element on the periodic table is composed of one type of atom. These atoms cannot be broken down into any simpler substance.
Atoms are composed of smaller subatomic particles such as the proton, neutron, and electron.
Atoms contain a nucleus surrounded by an electron cloud that consists of one or more energy levels.
The nucleus is a small, dense, center of which contains most of the atom’s mass
The nucleus contains the following subatomic particles:
Protons - positively (+) charged particles
Neutrons - particles that have no charge (neutral)

Both of these particles contribute to the atom's overall mass
The outside of the atom is comprised of the electron cloud
The electron cloud is an area outside of the nucleus where electrons are likely to be found orbiting (revolving, spinning) around the nucleus in several separate levels. Those levels are called energy levels.
Electrons are negatively (-) charged particles located in those energy levels surrounding the nucleus
There are many energy levels in the electron cloud. Electrons follow a specific order to fill these levels.
Lets take a closer look at the energy levels in the electron cloud..
These levels are like cups, and once the cups on the inside get filled, you have to start to fill the next cup.
The electrons that go into the last or outermost energy level get a special name.. They are called valence electrons.
We can tell a lot about an element by looking at the information given on the periodic table
The atomic number indicated here is the # of protons, contained in the nucleus of the atom. This number is also = to the atom's # of electrons.
The atomic mass indicated here is = to the # of protons + the # of neutrons.
The # of protons are always used to identify elements.
What is the # of protons also known as?
What other number could we say is equal to the atomic number?
The Atomic Number!
The # of electrons is equal to the atomic number!
What unit do we use to measure mass, when we measure with a triple beam balance?
More info on Atomic Mass
When measuring the mass of an atom, the unit we use is "Atomic Mass Units" or AMUs. Each proton and neutron have a mass of 1 AMU. Electrons have a mass of nearly 0 AMU.
So what would be the mass of an atom with 6 protons, 6 electrons and 4 neutrons?
10 AMU!
6 protons = 6 AMU
6 electrons = 0 AMU
4 neutrons = 4 AMU
Atomic Mass =
10 AMU
Grams!
Please draw this diagram at the top of your notes.
Tips when predicting the # of protons, neutrons, and electrons:
Atomic Number = # of Protons
and
# of Protons = # of Electrons
# of Protons MUST = # of Electrons because if not, then the atom would not be STABLE (which is very important!)

And lastly, we know that the Atomic Mass comes from what is found in the nucleus, so we know that Atomic Mass is = # of Protons + # of Neutrons

(always round atomic mass to the nearest whole number)
Tips for Atoms:
AN=P
P = E
AM = P + N
So how did we find out about all this stuff??
Well, there's been a lot of pretty important people who have been working on it.. And for a long time!
Skip to 40 seconds..
The earliest known scientist who "studied atoms" was Democritus.
He was a Greek philosopher who proposed the existence of the atom around 460 BC
He pounded materials until he made them into smaller and smaller parts.
Much like if we were to take a piece of paper and cut in half, then half again, then half again, etc.
When he first hypothesized about atoms, he called them atoma which is Greek for “indivisible”. He chose to call them this, because to our unaided eyes, they are virtually invisible. We can only learn about atoms if we break things down into smaller bits.
His Theory was that all atoms:
Are small hard particles
Are made of a single material formed into different shapes and sizes
Are always moving
Form different materials by joining together
The next known scientist who studied atoms was John Dalton.
He was a british chemist who, in 1803, he stated that
elements combine in specific proportions to form compounds
His Theory:
All substances are made of atoms that cannot be created, divided, or destroyed.
Atoms join with other atoms to make new substances.
Atoms of the same element are exactly alike, and atoms of different elements are different in mass and size.
His model looked like this:
JJ Thomson was the next scientist to study atoms
He was an English chemist and physicist who discovered the 1st subatomic particles
His Theory:
Atoms contain negatively charged particles called electrons and other positively charged matter.
Created a model to describe the atom as a sphere filled with positive matter with negative particles mixed in
Referred to it as the plum pudding model
And then, in 1912, there was Ernest Rutherford
Rutherford was a New Zealand physicist who first
discovered the nucleus of the atoms
His Theory:
There was a small, dense, positively charged particle present in nucleus called a proton
He also stated that electrons travel around the nucleus, but their exact places cannot be described.
One of the most widely used models was created by a Danish physicist in 1913. His name was Niels Bohr.
Bohr's research was the some of the most important up to this point, because he
discovered Energy Levels
.
Key parts of his theory were:
That electrons travel around the nucleus in definite paths and fixed distances.
Electrons can jump from one level to a path in another level.
Now I know you may think all this "Scientist Talk" has seemed long and dull... But you're not the first to think so!
Less than 100 years ago (1924), there was Erwin Shrodinger, who was an Australian Physicist.
He took Bohr's research on Energy Levels and developed the Electron Cloud model
His Theory:
The exact path of electrons cannot be predicted.
The electron cloud is where electrons can likely be found.
And lastly there was James Chadwick who, a short 80 years ago (1932),
discovered neutrons.
His Theory:
Neutrons have no electrical charge.
Neutrons have a mass nearly equal to the mass of a proton.
Unit of measurement for subatomic particles is the atomic mass unit (amu).
Please create this chart in your ISNs:
As we go through the rest of the prezi, I want you to fill in each side of this T-Chart. Write the name of the scientist on the left, and a key fact (what is in purple) on the right.
Modern Theory of the Atoms
The atomic theory that is used today, in Modern Science, is a combination of facts, discovered by each of the scientists we have discussed. The current theory states:
Atoms are composed of three main subatomic particles: the electron, proton, and neutron.
In stable atoms, the number of protons is equal to the number of electrons.
The protons and neutrons are located within the nucleus, while the electrons exist outside of the nucleus.
Valence electrons are the outermost electrons.
The type of atom is determined by the number of protons it has.
The number of protons in an atom is equal to the atomic number.
The sum of the number of protons and neutrons in a particular atom is called the atomic mass.
Most of the mass of the atom is concentrated in the nucleus of the atom.
So, let's do a quick review of the subatomic particles that make up atoms. This song is called "The Atoms Family!"
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