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## CHEMICAL FORMULEA

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**CHEMICAL FORMULEA**How chemical combinations are written.**A “formula” refers to how something is combined to make**a product.**A “formula” refers to how something is combined to make**a product. Elements (often referred to as chemicals) do not like to have any empty spaces in their outer valence shells, so they will react with other elements to somehow eventually get a full valence shell - by giving up electrons to another chemical, - by stealing electrons from another chemical, or - by sharing electrons with another chemical.**A “formula” refers to how something is combined to make**a product. Elements (often referred to as chemicals) do not like to have any empty spaces in their outer valence shells, so they will react with other elements to somehow eventually get a full valence shell - by giving up electrons to another chemical, - by stealing electrons from another chemical, or - by sharing electrons with another chemical. I’ll teach you about these different ways next week. For now, I want you to learn how we write these chemical combinations.**You’re probably familiar with some chemical formulae:**H20 = water CO2 = carbon dioxide**You’re probably familiar with some chemical formulae:**H20 = water CO2 = carbon dioxide Scientists use chemical abbreviations, parentheses, and placement of numbers to show how chemicals combine and in what ratios and attachments.**RECORD THE REST OF THE INFORMATION IN YOUR NOTES**TITLED “CHEMICAL FORMULAE”: ********************************************************************************* Formula * Atoms join/bond in ratios (“recipes”) in a way so that all atoms involved have full valence shells. They satisfy each other’s electron needs.**RECORD THE REST OF THE INFORMATION IN YOUR NOTES**TITLED “CHEMICAL FORMULAE”: ********************************************************************************* Formula * Atoms join/bond in ratios (“recipes”) in a way so that all atoms involved have full valence shells. They satisfy each other’s electron needs. Use of Letters: * Each element has its own unique abbreviation. Some just have 1 letter, some 2.**RECORD THE REST OF THE INFORMATION IN YOUR NOTES**TITLED “CHEMICAL FORMULAE”: ********************************************************************************* Formula * Atoms join/bond in ratios (“recipes”) in a way so that all atoms involved have full valence shells. They satisfy each other’s electron needs. Use of Letters: * Each element has its own unique abbreviation. Some just have 1 letter, some 2. * If two letters are used, the 1st one is capitalized and the 2nd letter is lower case.**Use of**Numbers: Subscripts = a little number written after and below a chemical abbreviation.**Use of**Numbers: Subscripts = a little number written after and below a chemical abbreviation. * this indicates how many of that element is involved with one bond.**Use of**Numbers: Subscripts = a little number written after and below a chemical abbreviation. * this indicates how many of that element is involved with one bond. example: H2O H = Hydrogen O = Oxygen The little 2 means 2 hydrogens bond with 1 oxygen**Use of**Numbers: Subscripts = a little number written after and below a chemical abbreviation. * this indicates how many of that element is involved with one bond. example: H2O H = Hydrogen O = Oxygen The little 2 means 2 hydrogens bond with 1 oxygen * a subscript can also be written after parentheses. The elements within parentheses are a “cluster” that can attach to another chemical. The subscript shows how many clusters were attached in the bond.**Use of**Numbers: Subscripts = a little number written after and below a chemical abbreviation. * this indicates how many of that element is involved with one bond. example: H2O H = Hydrogen O = Oxygen The little 2 means 2 hydrogens bond with 1 oxygen * a subscript can also be written after parentheses. The elements within parenteses are a “cluster” that can attach to another chemical. The subscript shows how many clusters were attached in the bond. example: Ba(NO2)2 Ba = Barium, N = Nitrogen, O = oxygen**Use of**Numbers: Subscripts = a little number written after and below a chemical abbreviation. * this indicates how many of that element is involved with one bond. example: H2O H = Hydrogen O = Oxygen The little 2 means 2 hydrogens bond with 1 oxygen * a subscript can also be written after parentheses. The elements within parenteses are a “cluster” that can attach to another chemical. The subscript shows how many clusters were attached in the bond. example: Ba(NO2)2 Ba = Barium, N = Nitrogen, O = oxygen NO2 sticks together as a cluster. It acts like one element.**Use of**Numbers: Subscripts = a little number written after and below a chemical abbreviation. * this indicates how many of that element is involved with one bond. example: H2O H = Hydrogen O = Oxygen The little 2 means 2 hydrogens bond with 1 oxygen * a subscript can also be written after parentheses. The elements within parenteses are a “cluster” that can attach to another chemical. The subscript shows how many clusters were attached in the bond. example: Ba(NO2)2 Ba = Barium, N = Nitrogen, O = oxygen NO2 sticks together as a cluster. It acts like one element. The little 2 outside the () shows there are two of these clusters attached to Ba Ba NO2 NO2**Big numbers * when chemicals combine, they are called**“molecules”**Big numbers * when chemicals combine, they are called**“molecules” * big numbers are used only in front of a formula to show how many molecules there are.**Big numbers * when chemicals combine, they are called**“molecules” * big numbers are used only in front of a formula to show how many molecules there are. example: 2 H2O The big 2 in front shows there are 2 water molecules.**Big numbers * when chemicals combine, they are called**“molecules” * big numbers are used only in front of a formula to show how many molecules there are. example: 2 H2O The big 2 in front shows there are 2 water molecules. H2O and H2O**PRACTICE:**Counting Atoms * Identify each element in the following formulae (abbreviations) * Write how many of each element exists as written.**PRACTICE:**Counting Atoms * Identify each element in the following formulae (abbreviations) * Write how many of each element exists as written. * Help each other – work with the person/people you share the table with. H2O2 2 H2SO4 Ca(SO4)2 2 Ca(SO4)2**PRACTICE:**Counting Atoms * Identify each element in the following formulae (abbreviations) * Write how many of each element exists as written. The subscript 2 says how many of the element directly in front of it. H = 2 O = 2 H2O2**PRACTICE:**Counting Atoms * Identify each element in the following formulae (abbreviations) * Write how many of each element exists as written. H = 4 S = 2 O = 8 The big 2 in front says there are 2 molecules, so you could show it like this: H2SO4 and H2SO4. In each molecule you would show: H = 2 S = 1 O = 4 Because there are 2 sets of these, you double the numbers. 2 H2SO4**PRACTICE:**Counting Atoms * Identify each element in the following formulae (abbreviations) * Write how many of each element exists as written. First, remember that an element can be represented with one or two letters, but the 2nd letter must be lower case so you can tell the difference between 1 or 2 elements. So Ca is one element. The 4 after the O says there are 4 O’s. The parentheses around SO4 says it’s a cluster that acts like 1 element. The subscript 2 after the parentheses says there are 2 of these clusters attached to Ca. It would look like this: Ca SO4 SO4 Now count everything. Ca(SO4)2 Ca = 1 S = 2 O = 8**PRACTICE:**Counting Atoms * Identify each element in the following formulae (abbreviations) * Write how many of each element exists as written. This is the same molecule you just tackled except there is a big 2 in front, meaning there are 2 molecules of Ca(SO4)2. It would look like this: Ca SO4 SO4 and Ca SO4 SO4 Look at the adjusted count for two molecules above left. 2 Ca(SO4)2 Ca = 2 S = 4 O = 16**Now it’s your turn!**Use your notes and your practice problems to solve the formulae on the Back of your notes. Work in your big teams in your lab stations and help each other figure the problems out! If you get stuck, send a runner to another team and they can come back to teach the rest of the group what they learned. Plus Equals