naming #5 naming molecular compounds. which comes first? the more positive of the 2 elements comes...
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NAMING THE ELEMENTS The more positive element is called by its name. The more negative element is called by part of its name and the ending ide. These are the same names as the anions of the elements have. e.g. oxide, sulfide, fluoride, chloride, bromide, iodide, nitride, hydride, selenideTRANSCRIPT
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NAMING #5Naming Molecular Compounds
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WHICH COMES FIRST?
The more positive of the 2 elements comes first. The more positive element is the one that is further to
the left and down on the periodic table. (i.e., the less
______________________ one comes first
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NAMING THE ELEMENTS
The more positive element is called by its name.
The more negative element is called by part of its name and the ending ide. These are the same names as the anions of the elements
have.
e.g. oxide, sulfide, fluoride, chloride, bromide, iodide, nitride, hydride, selenide
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If you are asked to write the name for this ionic compound- Al2S3 - you just say
___________________________________You do not need to say di or tri, because
aluminum in a compound is always _____, and
sulfur in an ionic compound is always ______, so
they must exist in a __________ ratio.
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However, in molecular compounds, the elements mostly don’t form
________________ charges, because the
electrons are_______________, not lost or gained.
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Example:What is the formula for phosphorous
chloride? The answer is:
__________________________________
There are 2 different compounds formed from phosphorous and chlorine. They are
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PREFIXES MUST BE USED You can not tell how many atoms of each element there is in a molecular compound (as you can by using the charges in ionic compounds). Therefore, you must put prefixes in the name to designate how many atoms of each element there is.
PCl3 = phosphorous trichloride PCl5 = phosphorous pentachloride
PREFIXES YOU MUST KNOWmono one pentafivedi two hexa sixtri three hepta seventetra four
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IMPORTANT RULE:
The first element only has a prefix if there are more than one of those atoms.
The second element always has a prefix.
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EXAMPLES – formulas to names
SF6
CO2
N2O4
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EXAMPLES – Name to formulas
sulfur trioxide
nitrogen trihydride
diphosphorous pentasulfide
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PRACTICE – Fill in the blanks
CCl4 ____________________________
Se3F7 ____________________________
SiS2 ____________________________
______________ carbon dioxide
______________ silicon tetrabromide
_______________ trinitrogen hexachloride