1. Elements, Atoms and Compounds
Earth Science 2.1A
Matter
Elements, Atoms and Compounds
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2. Matter
Everything in the Universe is made of matter.
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3. Matter On Earth, matter exists usually in three states
Solid: definite shape such as rocks
Liquid: definite volume but no definite shape
Gas: neither definite shape nor definite volume
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4. Matter
Most of Earth’s atmosphere is composed of the gases nitrogen and oxygen
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5. Elements
The names of many elements are common knowledge to us: gold, silver, copper, iron
An element is a substance that can not be broken down into simpler substances by chemical or physical means.
There are 112 known elements and new elements continue to be discovered to this day.
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6. Periodic table
Elements have been organized into their know properties by a document called the periodic table of elements
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7. Atomic Number
Each element is represented by a symbol with one, two or three letters
Each element has it’s atomic number at the top
The atomic number is the number of protons in the nucleus
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8. Periodic Table: periods & groups
Rows across in the Periodic Table are called Periods
The columns down in the Periodic Table are called Groups
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9. Periodic Table found in Earth’s Crust
Of the know elements, only 8 make up the Earth’s crust
Oxygen
Silicon
Aluminum
Iron
Calcium
Sodium
Potassium
Magnesium
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10. Atoms
An atom is the smallest particle of matter that contains the characteristics of an element.
The central region is called the nucleus
The nucleus contains protons (+) and electrons (-)
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11. Protons, electrons, neutrons
Protons are dense particles with positive (+) electrical charges
Electrons have negative (-) charges and are smaller
Neutrons are equally as dense as protons but have no charge, they are neutral in charge.
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12. Atoms
Most atoms have the “same number of protons and electrons” balancing out their charge to a neutral charge.
The positive and negative charges cancel each other out.
For each proton their must be an electron to remain balanced.
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13. Atoms
An electron is the smallest of the three fundamental particles in an atom
An electron has a mass of about 1/1836 of a proton or neutron
Electrons move about the nucleus so fast, that they create a sphere shaped negative zone, a cloud of negative charges called an electron cloud.
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14. Electrons
Electrons are located in regions of this cloud called energy levels.
Each energy level contains a “certain set number of electrons”
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15. Atoms: Mass Number
The Mass Number of an atom is the total mass of the atom: the protons plus the neutrons
Recall that the “mass of an electron” is so small that the number of electrons has no effect on the mass number of the atom.
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16. Atoms Not all atoms have equal numbers of protons and neutrons.
Atoms with the same number of protons but different numbers of neutrons are isotopes of an element
Isotopes of the same element are numbered using a convention called the mass number and with the elements name or symbol
Iron-54 and Iron-57 are both isotopes of iron.
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18. Nature of Matter: Atoms and Elements
Biology 2.1
Nature of Matter: Atoms and Elements
1/30/2010

19. Nature of Matter All matter consists of atoms
An atom is the smallest unit of matter that can not be broken down by chemical means.
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20. Atoms Atoms consist of three types of particles Electrons Protons
Neutrons
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21. Electron Cloud
The region around the nucleus that electrons may occupy at any time is called the electron cloud.
Electrons move so fast in their orbits, they create a cloud of movement around the nucleus.
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22. Nature of Matter
Electrons are negatively (-) charged so the electron cloud has a negative charge
Protons are positively charged (+)
Neutrons have no charge thus are neutral (0)
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23. Electrons, protons, neutrons
Because protons and electrons are oppositely charged, they attract one another.
Atoms typically have one proton for each electron so they cancel each other out and have no charge ( a neutral charge)
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24. Elements
An element is a pure substance made up of only one kind of atom.
There are more than 100 known elements and each is represented by a one, two, or three letter symbol.
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25. Table of the Elements
Here is the Periodic Table Of Elements which shows the elements made up of
one type of atom only!
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26. Elements Elements differ in the number of protons their atoms contain.
Atoms of the simplest element, hydrogen, contain one proton and one electron.
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27. Elements
The number of neutrons in a atom is often but not always equal to the number of protons in the atom.
Atoms of an element that contain different numbers of neutrons than protons are called isotopes.
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28. Elements We can model isotopes of the elements using magnets. Material
A non-magnetic tabletop. 1 disk magnet with one color, mine are painted white
2 disk magnets with a different color, mine are painted black, both sets of magnets should be the same size.
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29. Elements Deuterium To Do and Notice
The white magnet represents the proton and the black ones neutrons.
Place one proton on the table. This is the nucleus of hydrogen. See the image at right. Normally, hydrogen does NOT have a neutron! It is the simplest atom.
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Deuterium

30. Elements Deuterium To Do and Notice
Hydrogen has a stable isotope named deuterium, 2H, or 2D, with one proton and one neutron.
This represents a stable isotope.
The proton and neutron numbers are the same but normally hydrogen has NO neutron!
Therefore, this is an isotope but a stable one.
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Deuterium

31. Elements
Hydrogen has a radioactive isotope named tritium, 3H, with one proton and two neutrons.
Place one white and two black magnets on the table so that the white magnet attracts both black magnets.
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32. Elements
The row at the right represent the nucleus of tritium. Here we see the white washer representing a proton with a positive charge.
The two black washers represent the two neutrons.
The extra neutron shifts it from a stable isotope to a radioactive unstable isotope.
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33. Chemical Bonding
Atoms can join together with other atoms to form stable substances.
A compound is a substance made of the joined atoms of two or more different elements.
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34. Covalent Bonds
Covalent bonds form when two or more atoms share electrons to form a molecule.
Covalent bonding occurs in ceramics, glass, wood and other organic materials.
When atoms bond using covalent bonding, the atoms share electrons in their outer shell creating full shells for both.
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35. Covalent Bonds Covalent bonds give a very strong bond.
Diamond is a good example of a strong covalent bond and has a high melting point and is very hard.
A molecule is a group of atoms held together by covalent bonds.
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36. Ionic Bonds Sometimes atoms or molecules gain or loose electrons.
An atom or molecule that has gained or lost one or more electrons is called an ion.
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37. Ionic Bonds
Ions have an electrical charge because they contain an unequal number of protons and electrons.
An atom that has gained electrons is negatively charged (-). It has more electrons (-) than protons (+)
An atom that has lost electrons is positively charged (+). It has more protons (+) than electrons. (-)
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38. Ionic Bonds
Ions of opposite charge may interact to form an ionic bond.
An ion with an extra electron (a negative charge) will be attracted to an ion with more protons than electrons ( a positive charge).
For both to become stable, the negative ion with more electrons (-) will be attracted to the positive ion that needs electrons (+) and seek to give away it’s extra electrons.
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39. Ionic Bonds
This attraction of ions of opposite charge interacting to transfer electrons is an ionic bond.
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