1. Matter & Bonding Lesson # 2
Ionic Compounds

2. Ions
An ion is an atom or group of atoms with a charge, which can be positive or negative.
If an atom loses some of its electrons, it becomes positively charged (it is losing some of its negative electrons).
If an atom gains electrons, it becomes negatively charged.
Atoms gain or lose electrons when they are trying to combine, or bond, with other atoms, because electrons are being transferred between them.

3. Ions (continued)
When two or more atoms combine, the result is called a compound.
The atoms are attracted to each other because of their opposite charge. The reason this occurs is so that reactive elements become stable when combined. This attraction is called an intramolecular force.
Stable means that their outermost shell of electrons is completely full.

4. Characteristics of Ionic Compounds
Compounds tend to be hard, brittle solids at room temperature.
They tend to form organized crystals with high melting points, which easily dissolve in water.
They can weakly conduct electricity.
This is why a grain of salt looks like a perfect cube, that it only melts at 800°C, and why we have salt water!
Another name for salt is sodium chloride, which is the ionic bond between sodium and chlorine.

5. Magnesium + Oxygen

6. Aluminum + Fluorine

7. Ionic Charges
All elements have a certain ionic charge, which is also called the valence, or combining capacity.
Some only have one ionic charge possible, others have two or three.
Metals LOSE electrons to form positive ions
Non-metals GAIN electrons to form negative ions
The result is an electrically neutral compound, where the sum of the charges on the positive ions equals the sum of the charges on the negative ions.

8. Charges Group 1: 1+ (Li, Na, K) Group 2: 2+ (Be, Mg, Ca)
Group 3-12: Many different charges
(Transition Metals)
Group 13: 3+ (B, Al)
Group 14: 4+ or 4-
Group 15: 3- (N, P)
Group 16: 2- (O, S)
Group 17: 1- (F, Cl, Br, I)
Group 18: 0 (Ne, Ar)
*Write these on your periodic table along the top of the groups*

9. Examples Calcium + Iodine Iron (II) + Oxygen
Aluminum + Sulfur Silver + Phosphorus

10. Finding Charges on Transition Metals
To determine the charge of a transition metal that has more than one charge option, you must reverse the criss-cross rule, and check the non-metal to determine its original charge.
Fe2S3 CuF2

11. Finding Charges (continued)
NiP

12. Polyatomic Compounds
Polyatomic ions – groups of atoms that tend to stay together and carry an overall ionic charge.
These ions can combine with metals in the same way as before to form neutral polyatomic compounds.
Naming – metal first, followed by name of polyatomic ion makes the full name.
Ensure to write in the charge on metal cations that possess more than one charge.

13. Examples Sodium + Sulfite Aluminum + Nitrate
Magnesium + Hydroxide Lead (IV) + Carbonate

14. Acids
Acids are ionic compounds where hydrogen is always the positive ion (cation).
Hydrogen can bond to non-metal ions or polyatomic ions.

15. 1. Hydrogen + Non-Metal
When hydrogen pairs with an anion, the word "hydro" starts the naming (hydro indicates a lack of oxygen) and ends in "ic acid" instead of "ide."
For example, hydrogen + phosphorus = hydrophosphoric acid
These acids are also called binary acids.

16. Hydrogen + Non-Metal Examples
Hydrogen + Chlorine
Hydrogen + Sulfur
Hydrogen + Nitrogen

17. 2. Hydrogen + Polyatomic Ions
When hydrogen pairs with a polyatomic compound, there is no "hydro" before the naming (as polyatomic ions contain oxygen).
For example, hydrogen + phosphate = phosphoric acid
These acids are sometimes called oxyacids.

18. Hydrogen + Polyatomic Ion Examples
Hydrogen + Chlorate
Hydrogen + Sulfate
Hydrogen + Nitrate

19. Working Backward to Find Acid Formulas
Determine the formula for the following acids. Don’t forget that as soon as you see the word “acid”, you know you are starting with hydrogen.
Sulfuric Acid Hydrophosphoric Acid