chemical formulas & naming. what we already know o we have talked about pure substance being...
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Chemical Formulas &
Naming
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What We Already KnowO We have talked about pure
substance being broken down into elements and compounds
--more than one element combined is a compound
O We have talked about how to figure out the number of valence electrons an element has
O So, how do these things relate to forming a compound…why do the elements even want to hang out together?
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CompoundsA chemical formula tells us both the elements involved and how many of
each are necessaryAlBr3
In this case, one Aluminum and 3 bromine are present
If there is only one of something present then no subscript is used
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How many atoms are present in these compounds?
O NaHCO3
O H2SO4
O KNO3
Here’s a tricky one…O Mg(OH)2
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Mg(OH)2
In this case there is a hydroxide ion present (OH) and everything that is
inside the parenthesis has to multiplied by what is outside the
parenthesis
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Let’s try another one…
Mg(NO3)2
There is one MgThere are two NThere are 6 O
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Octet RuleO Atoms tend to want to
achieve the electron configuration of a noble gas which has eight electrons in is highest occupied energy level
O Atoms are willing to gain or lose an e- to achieve this
O Gaining or losing an e- causes the atom to then be a charged particle.
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IonsAn atom with no charge has an equal
number of protons and electronsSo what about atoms with a charge?
Its called an ionO Cation- A positively charged ion formed
by an atom’s loss of a valence electron.Example Na+
O Anion- A negatively charged ion produced by an atom gaining an electron.
Example Cl-
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Ions ContinuedO Monatomic ions is one element with
a charge
O Polyatomic ions is more than one element with a charge
Example: SO42-
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Which Elements Will Gain and
Which Will Lose Electron
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Combining ElementsIt is the tendency to lose or to gain electrons
that determine why elements combine a certain way
Although ions carry a charge they have to combine in such a way that their charge
cancels out.
Na+ Cl-
Sodium wants to lose an electron and Chlorine is more than happy to accept that electron
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The 5 Steps for writing anionic compound formula:
1. Write the symbols of the two elements.
2. Write the valence of each as superscripts.
3. Drop the positive and negative signs.
4. Crisscross the superscripts so they become subscripts.
5. Reduce when possible.
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Formula for boron oxide
1.Write the symbols of the two elements.
B O
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Formula for boron oxide
2. Write the valence for each element
B3+ O2-
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Formula for boron oxide
3. Drop the positive & negative sign.
B3 O2
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Formula for boron oxide
4. Crisscross the superscripts so they become subscripts.
B3 O2
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Formula for boron oxide
5. Reduce subscripts when possible.(not possible here)
B2O3
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Examples of Reductionof Subscripts:
Sr 2O2 SrO
Al3P3 AlP
Pb2O4 PbO2
Subscripts can only be reduced if they are divisible by the same
number
Reduces to
Reduces to
Reduces to
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Naming Ionic Compounds (Regular & Polyatomic)
1. Write the name of the cation (metal)
2. Write the name if the anion (nonmetal)
-If only 2 elements, cut off the ending of the 2nd element and add “ide”
-If a polyatomic ion, use the name the class copy data sheet gives you.
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Examples
1. NaCl
2. MgSO4
3. K3PO4
4. Ca(ClO3)2
5. NH4NO2
O Sodium chloride
O Magnesium sulfate
O Potassium phosphate
O Calcium chlorate
O Ammonium nitrite
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Naming Ionic Compounds (Variable Charge)
1. Check to see that these metal are in the d-block and have a variable charge
2. Write the name of the cation (metal) with (roman numerals which indicates charge)
3. Write the name of the anion (nonmetal or polyatomic ion)
4. The anion is named by adding –ide to the root of the element name
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Examples:O Lead (IV) OxideO Iron (II) sulfateO Cobalt (II)
chlorideO Copper (II)
phosphateO Zinc chloride
O PbO2
O FeSO4
O CoCl2O Cu3(PO4)2
O ZnCl2