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This review delves into the fundamentals of chemical formulas, focusing on elements, ions, and compounds. It explains that a formula with one capital letter represents an element from the periodic table. Positive ions are named after their elements (e.g., Na+ for sodium), while negative ions typically end in "-ide" (e.g., Cl- for chloride). The distinction between ionic and molecular compounds is also addressed, including naming conventions and the use of prefixes for non-metals. Key examples illustrate the formation of formulas from names, including both binary and polyatomic compounds.
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Elements If the formula has ONE CAPITAL LETTER, it is an element, and its name is what is found on the periodic table (regardless of subscript)
IONS Positive ions are named for the element Na+ is the ‘sodium ion’ Negative ions end in ‘-ide’ Cl- is the “chloride ion” Check table E for polyatomic ions (like NO3-)
all TWO element compounds (two capital letters) end in –IDE, whether molecular or ionic NF3 nitrogen trifluoride CaCl2 calcium chloride
MOLECULAR COMPOUNDS: - start with a NON-METAL - use PREFIXES in the name P2O5 diphosphorus pentoxide
IONIC COMPOUNDS: - start with a METAL - NO prefixes in name - if given name write SYMBOL and CHARGE above names to find formula
KF potassium fluoride Mg2+ P3- magnesium phosphide Mg3P2
If the metal can have more than one charge, use ROMAN NUMERALS in the name: Cu2+ Cl- copper (II) chloride CuCl2
if non-metal is POLYATOMIC ION, compound ends in –ITE or –ATE: KNO3 potassium nitrate Na2SO4 sodium sulfate
