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Elements & Atoms
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An atom refresher
Matter is anything that takes up space and has mass.
All matter is made of atoms
Atoms are the building blocks of matter, sort of how bricks are the building blocks of houses.
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An atom refresher
An atom has three parts:
Proton = positive
Neutron = no charge
Electron = negative
The proton & neutron are found in the center of the atom, a place called the nucleus.
The electrons orbit the nucleus.
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What are elements?
Elements are the alphabet to the language of molecules.
To make molecules, you must have elements.
Elements are made of atoms. While the atoms may have different weights and organization, they are all built in the same way.
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More about Elements..
Elements are the building blocks of all matter.
The periodic table is a list of all of the elements that can build matter. It’s a little like the alphabet of chemistry.
The periodic table tells us several things…
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Periodic Table
Atomic Number:
Number of protons and it is also the number of electrons in an atom of an element. 8
Element’s Symbol: An abbreviation for the element. O
Oxygen
Elements Name
Atomic Mass/Weight:
Number of protons + neutrons. 16
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7. Atomic Structure
Atoms have a nucleus that contains Protons and Neutrons
Electrons are contained in shells that surround the nucleus
An atom is made of mostly empty space
Protons have a positive charge
Electrons have a negative charge
Neutrons are Neutral

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Atom Models
There are two models of the atoms; however, we will be using the Bohr Model
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9. Bohr Models
Niels Bohr created a visual model of the atom to make them easy to understand
A Bohr Model contains a central nucleus surrounded by electron shells
For each model you state the number of protons and neutrons in the nucleus and draw a dot on the electron shells for each electron

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Bohr Model
The Bohr Model shows all of the particles in the atom.
In the center is circles. Each circle represents a single neutron or proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N.
In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e. - + + -
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11. Electrons have special rules….
You can’t just shove all of the electrons into the first orbit of an electron.
Electrons live in something called shells or energy levels.
Only so many can be in any certain shell.
The electrons in the outer most shell of any element are called valance electrons
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Nucleus
1st shell
2nd shell
3rd shell
Adapted from
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13. Valence Electrons
The electrons in the outer most electron shell are called valence electrons
The shell containing electrons that is furthest from the nucleus is called the valence shell
The number of electron shells with electrons is the same as the period number

14. Valence Electrons
Electron Shell
Number of Electrons 1 2 8 3 4 18 5 6 32 7
Each electron shell can hold a certain number of electrons
Electron shells are filled from the inside out
Noble Gases have full outer electron shells
All other elements have partially filled outer electron shells

15. Noble Gas Stability Noble gases are usually unreactive
This is because they have full valence shells
An element with a full valence shell is a happy element 
For two atoms to join together atoms must gain, lose or share electrons
Elements with full valence shells do not easily gain or lose electrons

16. Noble Gas Stability
Atoms want to gain stability
Atoms will try to gain or lose electrons to have a full valence shell
Metals try to lose electrons
Non-Metals try to gain electrons

17. Becoming An Ion Electrons are negatively charged
Protons are positively charged
Neutral atoms do not have a charge because the number of protons is the same as the number of electrons
When atoms gain or lose electrons they become positively or negatively charged
An atom with a charge is called an Ion

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So let’s try it….
How to draw a Lithium atom
First, look at the Periodic Table
Second, determine the number of protons the atomic number)
Then determine the number of neutrons (Atomic mass – atomic number)
Then determine the number of electrons the atomic number) 3 Li
Lithium 7
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So let’s try it….
Protons = 3 3 Li
Lithium 7 - + + + - -
Electrons = 3
2 in the 1st shell, 1 in the 2nd shell
Neutrons = 4
(7-3=4)
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Your activity…
When you are ready for your activity see your teacher.
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