Writing and Naming Compounds

ALL METALS have several characteristics:

have luster (shiny); some have more luster than others, but all metals have some shine. All metals are silvery or gray colored except gold and copper.

Will conduct electricity – some conduct better than others but all metals will conduct electricity to some degree; gold is considered to be the best electrical conductor, also silver, copper and aluminum

Ductile – can be pulled out into a wire Malleable - can be hammered into a thin sheet; some are more malleable

than others; gold is probably the most malleable, followed by silver and copper.

ALWAYS LOSE ELECRONS FROM THEIR OUTER ENERGY LEVEL TO FORM POSITIVE IONS WHIH ARE CALLED CATIONS. Since the positively-charged ion will be attracted to the negative electrode (opposites attract), the ion attracted to the cathode is called the CATION.

The Roman numeral at the top of the column on the Periodic Chart is the number of electrons in its outermost energy level, and these are the electrons which the metal will lose (all of them)

ALL NON-METALS have opposite characteristics

do not have luster and are frequently powdery, liquid or gaseous; most are colored

do not conduct electricity (non-conductors) except some of the metalloids which are used in computer chips

are not ductile are not malleable ALWAYS GAIN ELECTRONS INTO THEIR OUTER ENERGY

LEVEL UNTIL THEY HAVE 8 AND FORM NEGATIVE IONS WHICH ARE CALLED ANIONS. Since a negatively-charged particle will be attracted to the positive electrode (opposites attract), the ion which is attracted to the anode is called the ANION (opposites attract), the ion which is attracted to the anode is called the ANION.

The Roman numeral at the top of the column on the Periodic Chart is the number of electrons in that atoms outermost energy level, and non-metals must gain enough electrons here to make a total of 8 in the outermost energy level.

Positive ions (CATIONS) have more protons than they have electrons since metals ALWAYS LOSE electrons. This results in the ion having a positive charge.

Negative ions (ANIONS) have gained electrons in their outermost energy levels and therefore have more electrons than protons. This results in the ion having a negative charge.

OXIDATION NUMBER is the overall charge on an ion after it has lost

electrons (metals) or gained electrons (non-metals). Oxidation numbers can be determined by looking at the Periodic Chart for the “A” column elements, but usually it is easier just to memorize the oxidation number associated with every ion rather than having to look it up every time.

When ions are combined together to form compounds, THE OVERALL CHARGE OF THE COMPOUND WHICH RESULTS MUST BE “ZERO” OR NEUTRAL.

For example

if an ion of potassium (whose charge is +1) combined with an ion of chlorine (whose charge is -1), the compound that results is electrically neutral as written in a 1:1 ratio of ions i.e. 1 potassium ion with a charge of +1 will exactly neutralize 1 chlorine ion with a charge of -1, so the formula for the compound is written simply

KCl (1 K to 1 Cl)

However,

if an ion of magnesium (whose charge is +2 combined wit an ion of chlorine (whose charge is -1), the compound that forms must be electrically neutral, so therefore, it takes 2 of the chlorine ions (with a charge of -1 each) to neutralize 1 of the magnesium ions whose charge is +2.

When we write the number which shows us that there must be more than 1 of a particular ion present to make the compound neutral is always written as a SUBSCRIPT.

NOTICE THAT IN WRITING CHEMICAL FORMULAS, THE METAL ION IS ALWAYS WRITTEN FIRST AND THE NON-METAL ION IS WRITTEN LAST.

Write a correct formula for the compound, which would form between. (Criss – Cross Method)

lithium and fluorine calcium and sulfur cesium and oxygen aluminum and oxygen sodium and sulfur aluminum and chlorine potassium an oxygen

We will basically be writing and naming two different types of compounds—ionic and molecular, ionic compounds are those compounds which are made up of

a metal and a non-metal a metal and a polyatomic ion ammonium ion and a non-metal ammonium ion and a polyatomic ion

When naming BINARY (2 elements only) ionic compounds (i.e. a metal and a non-metal)

Call the entire name of the metal Shorten the name of the non-metal (usually

at the 2nd vowel from the end of the word) and

Add the suffix “ide”

Therefore KCl would be called potassium chloride, NOT potassium chlorine.

Name the following binary ionic compounds:

MgBr2

NaF Al2O3

CdO ZnS Na2O K3N

Some metals have more than one oxidation number and when you name them you must indicate which of the oxidation numbers you are using.

There are only 5 elements which you need to memorize which have more than one oxidation number and they are:

Iron (+3 or +2) Lead (+4 or +2) Tin (+4 or +2) Mercury (+2 or +1) Copper (+2 or +1)

some metals were found to have more than 2 oxidation numbers, so we adopted a new system of naming called the IUPAC (international union of Pure and Applied Chemists) which uses the element name and a Roman numeral (in parenthesis) written after the name. So, we can also name the compounds copper (1) and copper (II), iron (III) and iron (II), lead (IV) and lead (II), tin (IV) and tin (II), and mercury (II) and mercury (I)

Write correct formulas for the following

tin (IV) chloride iron (III) oxide

Covalent Compounds

Compounds can also be written which consist of TWO __NON METALS. In this case, one of the non-metals must assume a positive oxidation number. You do not need to worry about which of the non-metals is more likely to assume the positive oxidation number—you just need to be able to recognize that they are “special” compounds and therefore are named in a “special” way.

When two non-metals combine to form a compound, it is called a _MOLECULAR COMPOUND (Covalent).

Naming Covalent Compounds To name molecular compounds, we use a series of

prefixes to indicate the NUBER OF ATOMS OF EACH ELEMENT WHICH ARE PRESENT. These prefixed are not used at any other time in naming. They are:

1 – “mono” - only used in naming the second element 2 – di 3 – tri 4 – tetra 5 – penta 6- hexa 7 – hepta 8- octa 9 – nona 10 – deca

NAMING

If you wish to name Cl2O7 a molecular compound since it contains two non-metals, use the prefix to indicate how many chlorines are present and use the ENTIRE first element’s name (not shortened nor modified) – dichlorine. Then use a prefix to indicate how many atoms of the second element are present and shorten its name at the second vowel from the end of the name and add “ide” - heptaoxide.

Naming Compounds

Example: name the following molecular compounds

CO2

N2O3

Cl2O

SO3

CO