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WRITING AND NAMING IONIC COMPOUNDS. When atoms combine, it’s always in simple whole number ratios. The smallest unit of atomic combinations that retains the characteristics of the compound is a molecule.

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Writing and naming ionic compounds

WRITING AND NAMING IONIC COMPOUNDS


When atoms combine, it’s always in simple whole number ratios

The smallest unit of atomic combinations that retains the characteristics of the compound is amolecule


The composition of a molecule can be represented in two waysaseither anempirical formula or a molecular formula

C3H6

CH2

An empirical formula gives thesimplest ratioof atoms in a compound

A molecular formula tells how many

of each atom

are present

in the compound


A remarkable feature of com-pounds formed from elements is that the properties of the reactant elements islost

+


In order to become more stable an some atoms find it energetically fea-sible to either lose or gain valence electrons.

Atoms that lose e- are positive A.K.A. cation

Atoms that gain e- are negative

A.K.A. anion


We tend to focus specifically on the loss or gain of the outer s, p, (A.K.A. valence e-) ,and sometimes the d e- of unfilled d sublevels).

The valence e- an atom contains has a direct effect on the charge the atom develops as it forms an ionic bond.

We have a list of the common ionic charges developed during ionic bonding.


SOME COMMON CATIONS outer s, p, (A.K.A.

(Note: the names of many of the ions include Roman numerals. These numerals are known as the Stock system of naming chemical ions and elements)

+1

+2

+3

+4

Magnesium

Lead (IV)

Mg+2

Pb+4

Aluminum

Al+3

Lithium

Li+1

Vanadium (IV)

Ca+2

V+4

Chromium(III)

Cr+3

Sodium

Na+1

Calcium

Tin (IV)

Sn+4

Iron (III)

Cr+3

Potassium

K+1

Strontium

Sr+2

MONATOMIC IONS

Vanadium (III)

V+3

Rubidium

Rb+1

Barium

Ba+2

Cesium

Cs+1

Cadmium

Cd+2

Copper (I)

Cs+1

Chromium (II)

Cr+2

Silver

Ag+1

Cobalt

Co+2

Copper (II)

Cu+2

Iron (II)

Fe+2


SOME COMMON CATIONS outer s, p, (A.K.A.

(Note: the names of many of the ions include Roman numerals. These numerals are known as the Stock system of naming chemical ions and elements)

+1

+2

+3

+4

Lead (II)

Pb+2

Mn+2

Manganese (II)

MONATOMIC IONS

Mercury (II)

Hg+2

Nickel (II)

Ni+2

Tin (II)

Sn+2

Vanadium (II)

V+2

Zinc

Zn+2


SOME COMMON ANIONS outer s, p, (A.K.A.

(Note: the names of many of the ions include Roman numerals. These numerals are known as the Stock system of naming chemical ions and elements)

-1

-2

-3

-4

MONATOMIC IONS

Fluoride

Nitride

N-3

Oxide

F-1

Pb-2

S-2

Chloride

Cl-1

Sulfide

Phosphide

P-3

Bromide

Br-1

Iodide

I-1


-2 outer s, p, (A.K.A.

-3

+1

C

O

N

H

P

O

-1

3

O

H

4

4

There are also combinations of covalently bonded atoms that also have a charge called polyatomic ions

Poly- means many, but we treat each of these polyatomic ions as a single unit with a single charge


POLYATOMIC IONS outer s, p, (A.K.A.


POLYATOMIC IONS outer s, p, (A.K.A.


Today is all about combining these electrically charged ions together to form stable compounds.

Reminder: when two atoms combine transferring valence electrons it is called an ionic bond.

Oppositely charged ions attract each other and form an ionic bond that is electrically neutral, to establish a molecule that is neutral.


Looking at the structure of salt shows that the attraction between ions is so great that many sodium ions and chloride ions become involved.


The results of each ion being surrounded by several other ions allows the attraction between oppositely charged ions to be muchgreaterthan the repulsion between ions with thesame charge.

The strong attraction between the ions, & the orderly arrangement in the crystal affect the properties of the compound.


Cations & anions are pulled together in a tightly packed structure, giving each crystal a characteristic shape

The simplest repeating unit of anions and cations is called a unit cell.


Predicting the formation of ionic cmpnds structure, giving each crystal a

We can predict the combinations of ions and the formation of their ionic formulas, knowing how ions interact

We can have 2 different kinds of ionic compounds formed: binary or ternary


WRITING IONIC FORMULAS structure, giving each crystal a

There are a couple of rules to follow to make sure that the proper ionic formula is written.


RULE #1 structure, giving each crystal a

Ions will combine only inthe simplestwhole numberratiowhich cancels out the charge to form a neutral compound

The sum of the ions’ charges must be zero

3(+1) + (-3) = 0

+2 + (-2) = 0


RULE #2 structure, giving each crystal a

The compound formula is ALWAYS written with the cation first then the anion.

It’s better to be positive than negative 

NaCl

ClNa


+1 structure, giving each crystal a

-1

K

I

+

+2

-2

Mg

O

+

Some ionic compounds’ charges automatically cancel each other out.

KI

MgO


What if we were forming ionic compounds with ions whose charges don’t add up to a charge of 0?

How do we decide the proper ratio of cations and anions?


+3 charges don’t add up to a charge of 0?

-1

Al

Cl

+

+3

-1

AlCl

Al

3 Cl

+

3

=2

What if we had three chlorine ions for every one Aluminum ion?


+3 charges don’t add up to a charge of 0?

-2

Al

O

&

+3

-2

Al O

2 Al

3 O

&

3

2

We need to find the ratio

of ions that will make the charges cancel out to a neutral compound.


We have a trick that will help us know the number of the ions to make a neutral compound.

IT’S NOT A TRICK SO MUCH AS A SHORTCUT!


+3 ions to make a neutral compound.

-1

Al

Cl

AlCl

+

3

+2

-3

Ca

P

Ca

P

+

3

2

CRISS-CROSS RULE:


Using polyatomic ions ions to make a neutral compound.

To write the formulas for compounds containing polyatomic ions, follow the rules for writing formulas for binary compounds, with one additional consideration.

We add parentheses around the polyatomic ion when more than one of the ion is needed to develop the proper ratio.


-1 ions to make a neutral compound.

OH

+

+3

Al

Al(OH)

3

-2

+1

Na

SO

+

4

Na SO

4

2


Ca ions to make a neutral compound.+2 & O-2

Sn+4 & CO3-2

NH4+1 & SO4-2

Mg+2 & C2H3O2-1

Practice Writing Formulas

CaO

Sn(CO3)2

(NH4)2SO4

Mg(C2H3O2)2


NAMING THEM ions to make a neutral compound.

  • Most of the time you can name an ionic compound by

    • 1) Writing the name of the first element

    • 2) Writing therootof the name of the second element

    • 3) Adding-ideto the root


NAMING THEM ions to make a neutral compound.

CaCl2 

K3P 

Al2S3

Calcium chloride

Potassium phosphide

Aluminum sulfide


NAMING THEM ions to make a neutral compound.

Some of our metals have more than one ionic charge

  • We have to determine the charge on the metal

  • We then indicate the charge as a roman numeral


NAMING THEM ions to make a neutral compound.

FeCl2 

FeCl3

PbBr2

Iron(II) chloride

Iron (III) chloride

Lead (II) bromide


NAMING THEM ions to make a neutral compound.

If the compound has a polyatomic ion in it

1) name the first element, including the roman numeral if appropriate

2) then name the polyatomic ion


NAMING THEM ions to make a neutral compound.

Fe(OH)2 

Ca3 (PO4)2 

Na2SO4

Iron(II) hydroxide

Calcium phosphate

Sodium sulfate


Strontium Nitrite ions to make a neutral compound.

Sr(NO2)2

CuOH 

Copper (I) hydroxide

Lead (IV) phosphide 

Pb3P4

NH4OH 

Ammonium hydroxide

Sodium carbonate 

Na2CO3


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