2.5 Chemical Symbols & Formulassnc1p1mazza.weebly.com/.../chemical_symbols_and_formulas.pdf ·...
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Chemical Symbols & Formulas Copyright © 2010 McGraw-Hill Ryerson Ltd. In what ways do scientists communicate about elements and compounds? In what ways do scientists communicate about elements and compounds? Topic Topic 2.5 2.5 (Pages 130-9)
Transcript of 2.5 Chemical Symbols & Formulassnc1p1mazza.weebly.com/.../chemical_symbols_and_formulas.pdf ·...
Chemical Symbols & Formulas
Copyright © 2010 McGraw-Hill Ryerson Ltd.
In what ways do scientists communicate about elements and compounds?
In what ways do scientists communicate about elements and compounds?
Topic Topic 2.52.5
(Pages 130-9)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
In what ways do scientists communicate about elements and compounds?
In what ways do scientists communicate about elements and compounds?
• All of the compounds on Earth are built from the elements on the periodic table.
• The periodic table lists just under 120 elements, and only 80 of these commonly form compounds.
• Scientists think that there may be as many as 10200 different compounds. (That’s 1000000000000000000… and 183 more zeros)
The compounds that are just made up of carbon and hydrogen number in the millions!
Recall…
Element pure substance that is made up of 1 type of atom; identified by a chemical symbol e.g. Carbon
Atom smallest unit of matter; the building blocks of elements
Why Chemical Symbols?
These symbols are standard (constant) throughout the world (regardless of language)
e.g. “H” is the symbol for Hydrogen in English, German and Chinese
Recall
Compound pure substance made up of 2 or more elements that are chemically combined
e.g. water
Molecule atoms that are bonded together; the building blocks of compounds
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Compounds Made of Carbon and HydrogenCompounds Made of Carbon and Hydrogen
Carbon and hydrogen can combine to form a variety of compounds.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Elements: Atoms and MoleculesElements: Atoms and Molecules
Almost all elements exist as atoms. A few elements exist as molecules.
Chemical Formula use both chemical symbols and numbers.
the chemical symbol is written first
the number of atoms is shown as a subscript (written smaller and slightly below the written symbol)
Chemical formulas are used to represent the types and numbers of atoms in compounds.
Chemical formulas are used to represent the types and numbers of atoms in compounds.
Chemical formulas can also be used to represent compounds.
note: If only one atom of an element is present, the subscript 1 is not written.
Chemical formulas are used to represent the types and numbers of atoms in compounds.
Chemical formulas are used to represent the types and numbers of atoms in compounds.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Example of Common Household Compounds and Their FormulasExample of Common Household Compounds and Their Formulas
Hydrogen Peroxide
Sodium Hydroxide
Sodium Chloride
H2O2 NaOH NaCl
Let’s Practice!
How many elements?
What are they?
How many atoms of each
element are present?
Total # of atoms?
CH4methane
H2Owater
H2O2hydrogen peroxide
Try It!
To help your understanding of how atoms combine to form compounds, models of the compound can be drawn or constructed from a variety of materials.
Building Models of MoleculesBuilding Models of Molecules
Carbon Monoxide
(CO)
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Key Concepts to be reviewed:•Compounds are made of molecules
•Molecules are 2 or more elements bonded together
•Chemical symbols are used to represent elements
• Chemical formulas are used to represent the types and numbers of atoms in compounds
Topic 2.5 ReviewTopic 2.5 Review
