|
Rules of writing formulas:
- · positive ion is written first … this is usually a metal
- · negative ion is written second … this is usually a nonmetal
- · subscripts are used to show how many ions of each part are in the compound. They are used to balance the charge of the ions.
- · criss-cross method:
Examples: sodium oxide à sodium is the positive ion = +1
oxide is the negative ion = -2
therefore … it takes 2 sodium ions to balance the charge of the oxide
Formula = Na2O
calcium nitrate à calcium is the positive ion = +2
nitrate is the negative ion = -1
therefore … it takes 2 nitrates to balance the charge of calcium
Formula = Ca(NO3)2
aluminum sulfide à aluminum is the positive ion = +3
sulfide is the negative ion = -2
therefore … it takes 2 aluminum ions and 3 sulfide to balance the charge
Formula = Al2S3
Write the formulas for each of the chemical names.
- barium chloride
- potassium nitrate
- aluminum oxide
- silver bromide
- calcium sulfate
- magnesium fluoride
- zinc hydroxide
- barium carbonate
- sodium nitride
- lithium acetate
- cesium chlorate
- ammonium phosphide
- calcium hydroxide
- rubidium iodide
- silver sulfide
CHEMICAL FORMULAS
Key Words: chemical symbols
subscripts
ions
polyatomic ions
cation
anion
Important Information: You must remember these things when writing chemical formulas.
- · Write the name of the element that comes first in the name
- · Write the name of the element that comes second in the name, but take off the ending and add –ide
- · If the second part of the formula is a polyatomic ion, then write the name of the ion.
Examples: CaCl2 calcium chlorine à calcium chloride
MgO magnesium oxygen à magnesium oxide
ZnS zinc sulfur à zinc sulfide
NaOH sodium hydroxide (notice this is one of your
Polyatomic ions to know!!!)
Write a word name for each of the following formulas.
- LiOH
- BeF2
- SrS
- KNO3
- NaClO3
- AlP
- AgBr
- NH4OH
- ZnO
- CaSO4
- RbC2H3O2
- NaCl
- LiI
- AlN
- MgCO3
- K2SO4
|
