How Big Are Atoms? Five-hundred-million gold atoms lined up side-by-side would form a line as long as a $10 bill.

Look around your home and you’ll be amazed at the variety of chemicals in your cupboards and on your shelves.

In the bathroom, you’ll find water, soap, shampoo, and toothpaste - all chemicals.

In the basement or garage, you may find cleaning products, such as ammonia and bleach, and perhaps painting and gardening products.

In your kitchen, you’ll likely find table salt, baking soda, and baking powder.

Each of these compounds has a chemical name and a chemical formula.

The formula identifies which elements, and how much of each, are in the compound.

So, for example, table salt’s chemical name is sodium chloride and its formula is NaCl.

Baking soda’s chemical name is sodium bicarbonate and its chemical formula is Na(HCO3).

NAMING CHEMICAL COMPOUNDS Until the 18th century, no standardized system existed for naming chemicals. This created confusion because the names for chemical compounds varied from country to country and scientist to scientist.

For example, hydrochloric acid and muriatic acid refer to the same thing. If you didn’t know that, you might think they were two different chemicals. Today, some compounds are better known by their common name. Bleach, for instance, is almost always used instead of the chemical name aqueous sodium hypochlorite.

In 1787, a French chemist named Guyton de Morveau created a naming system, or nomenclature, for compounds. He decided to use the chemical name for each element in the compound, always putting the metal element first. For example, zinc and oxygen combine to form zinc oxide.

Since 1920, the International Union of Pure and Applied Chemistry (IUPAC) has been the body responsible for agreeing on the appropriate name for every chemical compound discovered.

INTERPRETING CHEMICAL NAMES AND FORMULAS FROM COMPOUNDS

If you know only the formula of a chemical compound, you can determine its chemical name. If you know only its name, you can determine its formula. Table salt’s chemical name, sodium chloride, indicates that the compound is made of one atom of sodium and one atom of chlorine Its chemical formula, NaCl, indicates this too.

One sodium atom combines with one chlorine atom to form the compound sodium chloride, which we call table salt

Now look at the formula for the compound water: H2O. Notice that next to the H is a small 2 as a subscript. (“Sub” means below.) The 2 indicates that there are two atoms of hydrogen to go with every atom of oxygen in water. Subscript numbers in a chemical formula indicate the number of atoms of the elements that must combine to form the compound. No subscript number indicates that only one atom of that element is needed.

In water, two hydrogen atoms join with each oxygen atom.

Compound Chemical Formula

Elements No. of Atoms of Each

Total No. of

Atoms

sodium chloride

NaCl

• sodium •chlorine

water

H20

• hydrogen • oxygen

1

1

1

2 3

2

INDICATING THE PHYSICAL STATE OF A COMPOUND Another common notation added to chemical compounds indicates the state of the chemical at room temperature. After the chemical formula, a subscript s for solid, l for liquid, or g for gas is shown in parentheses.

For example, sodium chloride is written as NaCl(s), water is written as H2O(l), and natural gas (methane) is written as CH4(g). For aqueous solutions (substances dissolved in water), a subscript aq in parentheses is added to the formula. So, if sodium chloride was dissolved in water, the resulting aqueous solution would be written as NaCl(aq).

Glucose C6H12O6 (s)

The chemical formula for glucose tells us that each molecule is made of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms and the (s) indicates it is a solid. 24 atoms in all.

Chemical Formula:

Common Name:

Hydrogen peroxide

Number of Elements:

2 – Hydrogen, Oxygen

H2O2 (aq)

Peroxide

Scientific name :

Number of Atoms of each element:

Hydrogen- 2 Oxygen- 2

2 elements 4 atoms

Chemical Formula:

Common Name:

sucrose

Number of Elements:

3 – Carbon, Hydrogen, Oxygen

C12H22O11 (s)

Sugar Scientific name :

Number of Atoms of each element:

Carbon-12 Hydrogen- 22 Oxygen- 11

3 elements 45 atoms

Chemical Formula:

Common Name:

sodium hydrogen carbonate

Number of Elements:

4 – Sodium, Hydrogen, Carbon, Oxygen

NaH(CO3) (s)

Baking soda Scientific name :

Number of Atoms of each element:

Sodium - 1 Hydrogen - 1 Carbon -1 Oxygen - 3

4 elements 6 atoms

Chemical Formula:

Common Name:

2-propanol

Number of Elements:

3 – Carbon, Hydrogen, Oxygen

CH3CH(OH)CH3 (l)

Rubbing alcohol Scientific name :

Number of Atoms of each element:

Carbon-3 Hydrogen- 8 Oxygen- 1

3 elements 12 atoms

Chemical Formula:

Common Name:

aspartyl-phenylalanine methyl ester

Number of Elements:

4 – Carbon, Hydrogen, Nitrogen, Oxygen

C14H18N2O5 (s)

Aspartame

Scientific name :

Number of Atoms of each element:

Carbon-14 Hydrogen- 18 Nitrogen- 2 Oxygen- 5

4 elements 39 atoms

Chemical Formula:

Common Name:

Magnesium Hydroxide

Number of Elements: 3 - Magnesium , Oxygen, Hydrogen

Mg(OH) 2(s)

Milk of Magnesia

Scientific name :

Number of Atoms of each element: 1 - Mg , 2- Oxygen, 2- Hydrogen

3 elements 5 atoms

Chemical Formula:

Common Name:

2-hydroxy-1,2,3- propanetricarboxylic acid

Number of Elements: 3 - Carbon , Hydrogen, Oxygen,

C3H4(OH)(COOH)3 (s)

Citric acid Scientific name :

Number of Atoms of each element: Carbon - 6, Oxygen - 7, Hydrogen - 8

3 elements 21 atoms

Sodium, shown in (a), is a metal. Sodium combines with chlorine gas in a violent reaction (b). The product is table salt, NaCl(s) (c).

Na + Cl 2 → NaCl 2 Na + Cl 2 → 2 NaCl

Sodium chloride is called an ionic compound. Ionic compounds are pure substances formed as a result of the attraction between particles of opposite charges, called ions.

Table salt is formed from positively charged sodium ions and negatively charged chloride ions.

Other properties of ionic compounds include: their high melting point, good electrical conductivity, and distinct crystal shape.

All ionic compounds are solids at room temperature.

In fact, table salt will not melt until it is heated to 801°C. When an ionic compound is melted or dissolved in water, it will conduct electricity.

This property of ionic compounds led to the study of electrochemical cells (cells that either convert chemical energy into electrical energy or electrical energy into chemical energy). And that work in turn eventually led to the invention of batteries.

“Ion” Origin

The word “ion” comes from a Greek word meaning “to go” or “wander.”

When the ionic compound is dissolved in water, the metal and nonmetal form an aqueous solution of ions. An ion is an atom or a group of atoms that has become electrically charged through the loss or gain of electrons. The following table shows some examples of ion charges for various elements.

Sodium – Ion charge 1 +

Sodium will lose 1 electron Sodium has 1 valence electron Think of it as being able to fill in 1 hole.

Sodium - Na Chlorine Cl

Chlorine – Ion charge 1 – Chlorine gain 1 electrons Chlorine has 7 valence electrons Think of it as having 1 hole.

The crystals in this table salt are held together by ionic bonds.

Ion Charges To indicate ions in written notation, a plus sign (+) or a minus sign (-) is placed to the upper right of the element symbol. This is a superscript position (super - means “above”). For example, a sodium ion is written as Na + and a chlorine ion as Cl -.

Naming Ionic Compounds 1. The chemical name of the metal or positive ion goes first, followed by the name of the non-metal or negative ion. 2. The name of the non-metal negative ion changes its ending to ide.

Hydrogen – Hydride Nitrogen - Nitride Phosphorus – Phosphide Oxygen – Oxide Sulfur – Sulfide Selenium – Selenide Fluorine – Fluoride Chlorine – Chloride Bromine - Bromide Iodine - Iodide

Lithium Fluoride

Lithium 1+ has 1 extra valence electron – can fill one hole

Fluorine 1- missing 1 valence electron – has one hole

Li F

2. Lithium + Oxygen

Lithium 1+ has 1 extra valence electron – can fill one hole

Oxygen 2 - missing 2 valence electrons – has two holes

Lithium 1+ can fill one hole – you need 2 Li atoms to fill 2 holes

Li 2 O Lithium Oxide

2. Lithium + Nitrogen

Lithium 1+ has 1 extra valence electron – can fill one hole

Nitrogen 3 - missing 3 valence electrons – has three holes

Lithium 1+ can fill one hole – you need 3 Li atoms to fill 3 holes

Li 3 N Lithium Nitride

Sodium Chloride NaCl

Sodium Sulfide Na2S

Sodium Nitride Na3N

Sodium Phosphide Na3P

Potassium Bromide KBr

Potassium Sulfide K2S

Potassium Nitride K3N

Beryllium Iodide Bel2

Beryllium Oxide BeO

Beryllium Nitride Be3N2

4

5

6

7

8

9

10

11

12

13

Calcium Fluoride CaF2

Calcium Oxide CaO

Calcium Phosphide Ca3P2

Magnesium Iodide MgI2

Magnesium Sulfide MgS

Magnesium Nitride Mg3N2

Magnesium Chloride MgCl2

14

15

16

17

18

19

20

Metals that have more than 1 ionic charge

Some elements with more than one ion charge: Titanium 3+ or 4+ Iron 3+ or 2+

Nickel 2+ or 3+

Copper 1+ or 2+

Lead 2+ or 4+

Gold 1+ or 3+

Mercury 1+ or 2+

Use Roman Numerals to indicate the charge used – I, II, III, IV, V, VI, VII, VIII

Titanium 3+ or 4+ , Iron 3+ or 2+ , Nickel 2+ or 3+ , Copper 1+ or 2+ , Lead 2+ or 4+

Gold 1+ or 3+ , Mercury 1+ or 2+

Roman Numerals to indicate the charge used –(1)  I,  (2)II,  (3)III,  (4)IV,  (5)V,  (6)VI,  (7)VII,  (8)VIII      

1.Titanium III Fluoride

Titanium IV Fluoride

2.Titanium IV Oxide

Titanium III Oxide

Ti 3+ F 1-

One atom of titanium will fill 3 holes

One atom of fluorine will has 1 hole to fill

Ti F3

Ti 4+ F 1-

One atom of titanium will fill 4 holes

One atom of fluorine will has 1 hole to fill

Ti F4

Ti 4+ O 2-

One atom of titanium will fill 4 holes

One atom of oxygen will has 2 holes to fill

Ti O2

Ti 3+ O 2-

One atom of titanium will fill 3 holes

One atom of oxygen will has 2 holes to fill

Ti + O - 3 2

Ti O

 

3. Titanium III Nitride .

Titanium IV Nitride 4. Iron III Chloride Iron II Chloride 5. Iron III Sulfide Iron II Sulfide 6. Copper I Oxide Copper II Oxide

Ti N

Ti3N4

FeCl3

FeCl2

Fe2S3

FeS

Cu2O

CuO

 

8. Lead II Fluoride Lead IV Oxide 9. Gold I Oxide Gold III Nitride 10. Mercury I Oxide Mercury II Nitride

Pb F2

PbO2

Au2O

AuN

Hg2O

Hg3N2

Polyatomic Ions Some ions can also form when certain atoms of elements combine.

These ions are called polyatomic ions (poly - means “many”). Polyatomic ions are a group of atoms acting as one. The formula is written in brackets. The name will not end in ide. Ammonium (NH4)1+

Bicarbonate (HCO3)1- Hydroxide (OH)1- Nitrate (NO3)1-

Nitrite (NO2)1- Carbonate (CO3)2- Sulfate (SO4)2- Sulfite (SO3)2-

Phosphate (PO4)3-

Polyatomic Ions

Ammonium (NH4)+

Cations (+1 Charge)

Polyatomic Ions

Bicarbonate (HCO3)-

Anions (-1 Charge)

Polyatomic Ions Anions (-1 Charge)

Hydroxide (OH)-

Polyatomic Ions

Nitrate (NO3)- Anions (-1 Charge)

Nitrite (NO2)-

Polyatomic Ions

Carbonate (CO3)2-

Anions (-2 Charge)

Polyatomic Ions

Sulfate (SO4)2-

Anions (-2 Charge)

Sulfite (SO3)2-

Polyatomic Ions

Phosphate (PO4)3-

Anions (-3 Charge)

 

1. Ammonium + Fluorine 2. Ammonium + Oxygen 3. Ammonium + Nitrogen 4. Sodium + Hydroxide 5. Magnesium + Hydroxide

Ammonium Fluoride (NH4)F

Ammonium Oxide

(NH4)2O

Ammonium Nitride

(NH4)3N

Sodium Hydroxide

Na(OH)

Magnesium Hydroxide

Mg(OH) 2

 

6. Calcium + Nitrate 7. Potassium + Nitrite 8. Lithium + Carbonate 9. Potassium + Sulfite 10. Calcium + Phosphate

Calcium Nitrate

Ca(NO3) 2

Potassium Nitrite

K(NO2)

Lithium Carbonate

LI2(CO3)

Potassium Sulfite K2(SO3)

Calcium Phosphate

Ca3 (PO4)2

 

11. (NH4) 2O 12. Ca (OH) 2 13. K 2 (SO4) 14. K3 (PO4) 15. Be (OH) 2

Ammonium Oxide

Calcium Hydroxide

Potassium Sulphate

Potassium Phosphate

Beryllium Hydroxide

Bonus  –  Metals  with  more  than  1  charge    16. Cu(OH)2 17. Fe 2 (SO4)3 18. Hg3(PO4)2 19. Pb(OH)2

Copper II Hydroxide

Iron III Sulfate

Mercury II Phosphate

Lead II Hydroxide

When non-metals combine, a pure substance called a molecule or a molecular compound is formed.

Molecular compounds differ from ionic compounds in several ways.

They can be solids, liquids, or gases at room temperature. They tend to be insulators, or poor conductors of electricity. They also have relatively low melting and boiling points because the forces between the molecules are weak. Examples of molecular compounds: sugar, acetylene, and water.

Scientists have discovered more than 10 million compounds. At least 9 million are molecular compounds containing the element carbon.

WRITING FORMULAS FOR MOLECULAR COMPOUNDS Writing formulas for molecular compounds is similar to writing formulas for ionic compounds, except that no ions are present and the ion charge is not used in the formulas. This makes it hard to predict how non-metals combine. However, the formulas still clearly show what elements are present, and how many of each type of atom make up the molecule. For example, hydrogen gas is usually found as H2. Each molecule has two atoms of hydrogen connected to each other. For ammonia ( NH3(g) ), the situation is similar. Three hydrogen atoms combine with the nitrogen atom.

Naming of Molecular Compounds

Non-metal + Non-metal 1. The first element in the compound uses the element name

(just like the ionic compounds do). 2. The second element has a suffix – ide (like the ionic compounds).

3. A prefix is used which tells how many atoms there are.

4. Exception to #3 above – when the first element has only 1 atom the prefix mono is not used.

Examples: CO2 carbon dioxide CO carbon monoxide CCl4 carbon tetrachloride H2O Dihydrogen monoxide

Number of Atoms Prefix 1 mono 2 di 3 tri 4 tetra 5 penta 6 hexa 7 hepta 8 octa 9 nona

10 deca

Molecular Compounds – Non-metal + Non-metal CO2 N2O N2O3 NF3 CCl4 PF5

Carbon dioxide

Dinitrogen monoxide

Dinitrogen trioxide

Nitrogen trifluoride

Carbon tetrachloride

Phosphorus pentafluoride

a. disulfur tetrafluoride

b. carbon trioxide

c. nitrogen pentoxide d. nitrogen tribromide e. dinitrogen heptachloride

f. carbon tetrachloride

g. hydrogen monochloride h. trihydrogen monophosphide

i. dihydrogen monoxide

S2F4

CO3 NO5

NBr3

N2Cl7

CCl4 HCl

H3P

H2O

Comparing Ionic And Molecular Compounds