1. Introduction to Atoms
Science 9, 2016

2. Models, Theories, and Laws
Read pg and write down important points

3. We have discovered approx. 90 elements that occur naturally on Earth
Recently, scientists have made more than 25 new elements artificially
Elements are sorted into three classes
Metals
Non-metals
Metalloids

4. Most elements are metals Most are shiny and silver or grey in colour
Excellent conductors of electricity and heat
Can be malleable and ductile
Metals like sodium will react explosively with water, but platinum will not react even if it is mixed with strong acids
Almost all metals are solid at room temperature
Can you think of an exception?

5. Many metals are too weak to be used alone
Combining Metals
Some metals have a low melting point so they can be moulded into a variety of shapes
Many metals are too weak to be used alone
“tin” cans are actually just coated with tin
Solution of two or more metals is called an alloy
White gold is an alloy, it combines gold with a white metal such as nickel or manganese
Examples of alloys?

6. 17 of the known elements are non-metals
Aren’t grouped because of similarities, grouped because they lack metal qualities
11 of them are gas at room temp
5 are solids
Bromine is red brown liquid
They are brittle and not malleable
Do not conduct heat or electricity well

7. Elements with metallic and non-metallic properties
Metalloids
Elements with metallic and non-metallic properties
Conduct electricity, but not very well (semiconductors)
Easier to control flow of electricity through semiconductors than conductors so they are often used in electronic devices
Silicon is most common metalloid
Pure silicon is rare but in combination with other elements it makes up sand and other compounds
About 40% of the mass of any rock comes from silicon
Is a major component of glass

9. Element Symbols Many languages have their own name for elements
To aid in communication, chemists agreed to use the same set of symbols for the elements
Many element symbols are based on Latin names
Silicon: Si
Silvers Latin name is argentum so it got the symbol Ag
Symbol consists of one or two letter
First letter is ALWAYS a capital and the second letter is not a capital
Example: is cobalt Co or CO?

10. Common Elements
Humans have been highly influenced by availability of certain elements
Iron age began several thousand years ago
When carbon was added to iron, steel was formed
Hydrogen and Oxygen combine to make water
Sodium and chlorine combine to form NaCl

11. Very strong when combined with carbon
Iron (Fe)
Silver/grey in colour
Malleable when heated
Very strong when combined with carbon

12. Pure carbon exists in several forms like graphite and diamond
Carbon (C)
Pure carbon exists in several forms like graphite and diamond
Both are formed underground as organism remains compress
C atoms connected differently
Diamond is hardest natural substance known
Coal is a black solid composed mostly of carbon in the form of graphite
One of main building blocks of life. Why???

13. Most common element in the universe
Hydrogen (H)
Most common element in the universe
Makes up most of the atoms in the stars
Simplest and lightest atom
Almost all hydrogen on earth is present in water
Pure hydrogen occurs in nature as a gas
Extremely flammable
The idea of a thermonuclear fusion bomb ignited by a smaller fission bomb was first proposed by Enrico Fermi to his colleague Edward Teller in 1941 at the start of what would become the Manhattan Project.

14. Sodium (Na)
Shares properties with iron
Conducts electricity and are shiny
Iron reacts slowly with oxygen and moisture to form rust whereas sodium reacts quickly and violently if exposed to air or water
Pure sodium is usually stored in oil where it can remain without reacting for a ling time
So soft that a knife can easily cut through it

15. Pure oxygen is gas at room temp
Oxygen (O)
Pure oxygen is gas at room temp
Makes up approx. 21% of the air we breathe
The air we breathe is two Oxygens bonded together
Most oxygen comes from plants and algae which produce oxygen while using sunlight to produce sugar
Ozone is three oxygens bonded together
Toxic for living organism to breathe and is a pollutant when close to ground
In upper atmosphere, ozone forms a layer that absorbs UV light

16. Most common element on Earths surface
Oxygen (O)
Most common element on Earths surface
Makes up more than 50% of the mass of most rocks
Rocks are ground up to form sand which can be melted to form glass
Most atoms in glass are oxygen atoms

17. Have properties that make them potentially useful…….. and hazardous
Compounds
A pure substance made up of two or more elements that are chemically combined
Have properties that make them potentially useful…….. and hazardous
Two types of compounds
Ionic
Molecular

18. Ionic Compounds
Pure substances which usually consist of at least one metal and one non- metal
Most ionic compounds:
Have high melting points
Form crystals
Dissolve in water to form solutions that conduct electricity
Are solid at room temperature

19. Forming Ionic Compounds
When elements combine to form an ionic compound, an atom will lose or gain electrons to form an ion with an electric charge
Metals tend to lose an electron, making them a positive ion
Many non-metals can gain electrons, making them a negative ion

20. Some metals can form more than one type of ion
Ions
Some metals can form more than one type of ion
Example: Iron can lose two electrons and have a 2+ charge or it can lose three electrons and have a 3+ charge
Sometimes a group of atoms of different elements with an overall electric charge acts as a single ion
This is a polyatomic ion
Example: NH4+

21. Positive and negative ions attract each other
Ionic Bonding
Positive and negative ions attract each other
Attraction between atoms or ions is called a bond
Attraction between ions of opposite charges is called an ionic bond
Ionic bonding is not one directional, ions are arranged in a crystal lattice
Each ion is attracted by more than one ion in its neighbourhood

22. Pure substances usually formed when non-metal elements combine
Molecular Compounds
Pure substances usually formed when non-metal elements combine
Atoms join together by sharing electrons in their highest energy level to form small groups to form small groups called molecules
A molecule is the smallest amount of a pure substance that can exist
Examples:
Table sugar
Water
Hydrogen Peroxide

23. Properties of Molecular compounds
Can be solids, liquids, gases at room temperature
Are usually good insulators
Have relatively low boiling points

24. The sharing of electrons between atoms is called a covalent bond
Covalent Bonding
The sharing of electrons between atoms is called a covalent bond
Molecule is a neutral group of atoms held together by covalent bonds
Diatomic molecules
For some elements, each atom of the element shares electrons with another atom of the same element to form a stable molecule
Example?

25. Chemical Names and Formulas
Every compound has a chemical name and formula
Chemical formula identifies which elements, and how many atoms or ions of each, are in the compound
The subscript number indicates how many atoms of a specific element are in a molecule
H+H+O=H20