6.2 names and formulas of chemical compounds...

6.2 Names and Formulas of Chemical Compounds

Friday February 28, 2014.Part 1

Tuesday, March 4, 14

Common Name Chemical Name Chemical Formula

vinegar acetic acid CH3COOH

table salt sodium chloride NaCl

chalk calcium sulphate CaSO4

baking soda sodium hydrogen carbonate

NaHCO3


• each chemical compound has an official chemical name, even though you may know them by the common name

• the chemical formula identifies the number of each element in the compound

• for example, baking soda’s chemical name is sodium hydrogen carbonate, and its chemical formula is NaHCO3 (meaning there is one Na, one H, one C and three O’s in each molecule of baking soda)


• the ion notation contains the symbol for the element and a superscript number and + or - sign

• example: lithium - Li+ (remember, ions with a 1+ or 1- charge don’t need the “1”)• What is the ion notation of:‣beryllium? ‣nitrogen? ‣sulphur?

Be2+

N3-

S2-


Element Ion Charge Ion notation

hydrogen 1+ H+

oxygen 2- O2-

fluorine 1- F-

magnesium 2+ Mg2+


RULES (MEMORIZE THESE!):1.Name the metal ion first: The name of the metal ion is the same as the element name. For example, in NaCl, the name of the sodium ion (Na+) is “sodium”.

2.Name the non-metal ion second: When a non-metal becomes a negative ion, the ending of its name changes to “-ide”. For example, a chlorine atom (Cl) gains an electron to become a chloride ion (Cl-).

3.Combine these two parts for the complete name: For example the name of NaCl is “sodium chloride”.


Formula Positive Ion

Negative Ion

Name

MgO Mg2+ O2- magnesium oxide

BaF2 Ba2+ F- barium fluoride

K3N K+ N3- potassium nitride


WRITING IONIC FORMULAS

example #1: calcium + chlorineIn order to figure out how many of each element you’ll need to make a compound, draw the Lewis diagrams

(remember last week?!)

Ca Clx x

xxxx

xClx x

xx

xxx

CaCl2 (calcium chloride)



example #2: aluminum + oxygen

Al OOx x

xxxx

x x

xx

x x

Al Ox x

xxxx

Al2O3(aluminum oxide)



CaCl2Hmm...notice something?

Charge on: Ca2+ Cl-CRISS CROSS RULE!

Why does this work?The charges even out!

1(2+) Ca Cl

Look back at the formula: + 2(1-) = 0!



Al2O3

Charge on: Al3+ O2-

CRISS CROSS RULE!

2(3+) Al O

Look back at the formula: + 3(2-) = 0!



example: calcium + chlorine

1. Write the element symbols with the metal ion written first. Ca Cl2. Take the number of the charge on the non-metal ion and make it a subscript on the metal ion (if it’s 1, you can just leave it without a number).

Ca2+ Cl-

Ca Cl3. Take the number of the charge on the metal ion and make it a subscript on the non-metal ion (if it’s 1, you can just leave it without a number).

CaCl2



elements ions formula namepotassium and

iodine K+, I- KI potassium iodide

magnesium and chlorine Mg2+, Cl - MgCl2 magnesium chloride

rubidium and phosphorus Rb+, P 3- Rb3P rubidium phosphide

beryllium and sulfur Be2+, F- BeF2 beryllium fluoride

aluminum and nitrogen Al3+, N 3- AlN aluminum nitride

When the elements have the same charge value (the number), you can cancel the numbers out....



example: aluminum + nitrogen

Al Nx x

xx

x

AlN


• elements like iron, copper, and lead can form an ion in more than one way: these are multivalent ions• in this case, a Roman numeral is included in the ion’s name to show the ion’s charge• example: the name Fe2+ is iron (II) which is read “iron two”. The “two” refers to the charge. Similarly iron (III) is read “iron three” and named the Fe3+ ion.


1 I

2 II

3 III

4 IV

5 V

6 VI


WRITING IONIC COMPOUND FORMULASWITH MULTIVALENT IONS

example: iron (III) oxide

1. Write the ion for the metal. Fe3+

2. Write the ion for the non-metal. O2-

3. Use the criss-cross rule to find the formula. Fe2O3

example: chromium (II) chloride CrCl2lead (IV) nitride Pb3N4


NAMING IONIC COMPOUNDSWITH MULTIVALENT IONS

example: Cu3N2

1. Look at the subscript number on the non-metal ion. This is the positive charge on the multivalent ion.

Cu2+

2. Name that ion. Specify the charge using Roman numerals. copper (II)

3. Name the other ion. Add “ide” to the ending.

copper (II) nitride

example: FeCl3copper (II) oxideiron (III) chloride

CuOTuesday, March 4, 14

POLYATOMIC IONS• a group of atoms, made of more than one element, that act as a single ion


NAMING POLYATOMIC IONS

example: NaOH1. Name the metal. sodium2. Name the polyatomic ion. DO NOT CHANGE THE NAME.

sodium hydroxide

• HINTS:

• the polyatomic ion is often in brackets like Al(OH)3

• if there is more than one element after the metal, it’s probably polyatomic: CuSO4


names of elements or polyatomic

ions

ion notation formula chemical

name

potassium and hydroxide K+, OH - KOH potassium hydroxide

copper (II) and nitrogen Cu2+, N3- Cu3N2 copper (II) nitride

iron (III) and sulphate Fe3+, SO42- Fe2(SO4)3 iron (III) sulphate

barium and chlorate Ba2+, ClO3- Ba(ClO3)2 barium chlorate

lithium and nitrate Li+, NO3- LiNO3 lithium nitrate

CAUTION: Watch for Polyatomics and Multivalents!


1 = mono2 = di3 = tri4 = tetra5 = penta

WRITING NAMES FOR MOLECULAR COMPOUNDS

6 = hexa7 = hepta8 = octa9 = nona10 = deca


WRITING NAMES FOR MOLECULAR COMPOUNDS


WRITING FORMULAS FOR MOLECULAR COMPOUNDS


6.2 names and formulas of chemical compounds...

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