naming and formula writing. chemical formulas molecular: indicates the numbers of each atom in a...
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Naming and Formula Writing
Chemical Formulas
• molecular: indicates the numbers of each atom in a compound
C6H12O6
notation with numbers & symbols to show composition of a compound
• empirical: gives simplest whole-number ratio of atoms of elements
CH2O
• structural: indicates how the atoms are bonded to each other
Molecules• monatomic: single atoms of the same
elementEx: He, Ne, Kr, Xe, Rn (noble gases)
(the 1 subscript is understood)• diatomic: two atoms of the same element
Ex: H2, O2, N2, Br2
• more than two atoms of the same elementEx: P4 & S8
• two or more atoms of different elementsEx: H2O, NH4, CO2
Charges on all the atoms that make up a compound must add up to zero
Crisscross method for writing the formulas of binary ionic compounds
• the charge of each ion becomes the subscript for the other ion
(without + / - signs)• use simplest whole-number subscripts
Ex: calcium bromide Ca+2 + Br-1 CaBr2
• *same with polyatomic ions, but put
polyatomic ion in parentheses
Ex: calcium hydroxide Ca+2 + OH-1 Ca(OH)2
Some ions can exist with different charges (Fe+2 or Fe+3)
• remember that charges must = zero
• look at name to figure out charge
Ex: iron II chloride Fe? + Cl-1 FeCl2
Practice
• Strontium oxide calcium sulfide• Potassium carbonate lead (II) sulfate• Magnesium sulfide copper (I) chlorate• Strontium nitrate dihydrogen monosulfide• phosphorus pentachloride calcium
chloride• Sodium sulfide rubidium sulfide• Iron (III) chlorate
Rules for Naming Compounds
Basic Rule:
1) Name the first element in the compound
2) Name the second element by changing the ending of the name to –ide
OR if the compound is made up of more than 2 elements, you have a polyatomic ion and you will use the polyatomic ion’s name with no changes
Naming a Metal and a Nonmetal
• Basic rule—no changes
Ex: NaCl sodium chloride
CaSO4 calcium sulfate
Naming Compounds with transition metals
• Basic rule with one change:– Find the charge of the transition metal
(the charge of a transition metal can change)– Write the charge after the transition metal’s
name (in Roman numerals)
Ex CoI2 cobalt (II) iodide
Fe(ClO3) 3 iron (III) chlorate
Naming 2 nonmetals• Basic rule with one change:
– Look at the number of atoms for the second nonmetal and select the correct prefix to add to the name:Prefix Meaning
mono- 1
di- 2
tri- 3
tetra- 4
penta- 5
hexa- 6
2 nonmetals (continued):Ex CO carbon monoxide
CO2 carbon dioxide• If the 1st element in the compound has more
than one atom, a prefix must be added to the first element’s name also
2nd elment always gets a prefix,1st element only gets a prefix if more than one atom
Ex P2S3 diphosphorus trisulfide
N2O5 dinitrogen pentoxide• Usually you won’t have 2 vowels together
– Exceptions: di-, tri-, tetra-, & penta- iodide and oxide
Practice• CaS NiCl
• MgCl2 SiCl4• Zn(NO3)2 K2CO3
• Hg(C2H3O2)3 Li2SO4
• LiBr PCl5• H2O PbSO4
• SrO CF4
• Ag(CrO4) 2 CS2