7.2 Ionic Bonding

Whena metal loses its valence electrons, it becomes positive charged ion called cation, while the none metal accepts these valence electrons and it becomes negative charged called an anion.

There are electrostatic forces causing the cation and anion attracted to each other.

Reference Ionic Bonds

Reference:Ionic Bonding

Forming an Ion

An example for an ion formation is sodium cation. Neutral sodium Na has 11 protons and 11 electrons. When Na loses an electron, number of the protons does not change but number of electrons will be less by one electron. The number of electrons will be 10 electrons and therefore, Na will have one positive charge. Na ⁺

 Figure 7.19 Formation of Na⁺ Ion

Ref: commons.wikimedia.org/

The none metal chlorine Cl has 17 protons and 17 electrons. When the chlorine atom gains an extra electron, the number of the protons does not change but number of electrons will be increased by one electron. A negative ion of chlorine called anion is formed as shown below:

Figure 7.20 Formation of Cl^– Ion

Ref: commons.wikimedia.org/

Forming an Ionic Bond

The video below illustrates the formation of an ionic bond. Once the oppositely charged ions form Na⁺ and F ^–, they are attracted by their positive and negative charges and form an ionic compound. Ionic bonds are also formed when there is a large electronegativity difference between two atoms. This difference causes an unequal sharing of electrons such that one atom completely loses one or more electrons and the other atom gains one or more electrons, such as in the creation of an ionic bond between a metal atom (sodium) and a nonmetal (fluorine).

Reference:Formation of Ionic Compounds

Naming an Ionic Compound from a Formula

1. Start naming the metal cation for example Ba ²⁺ (barium cation)
2. Then follow the name of the metal cation with the name of the none metal anion.
3. Discard the ine ending of the none metal chlorine and replace it with the ide ending

The name of the ionic compound ion BaCl₂ is called barium chloride.

Determining the Formula of Ionic Compound with Metal has one positive charge from a Name

Example:

Barium chloride

1.Barium is found in second group 2A. According the periodic table barium has +2 positive charges Ba  ²⁺. See figure below:

2.Chlorine anion called chloride has one negative charge Cl ^–_.

3. Now, one has to swap the values of the charges of the ions only not the signs of ion:

Ba cation will take the value 1 as subscript and the chloride will take the value of 2 as subscript:

Ba₁ Cl₂ which is written as BaCl₂.  The value of 1 is understood but it is not written.

Figure 7.21 Nomenclature of Ionic compound

Ref: commons.wikimedia.org/

Reference: https://chem.libretexts.org/Courses/College_of_Marin/CHEM_114%3A_Introductory_Chemistry/05%3A_Molecules_and_Compounds/5.07%3A_Naming_Ionic_Compounds

Figure 7.21 Charge of Ions from Periodic Table

Reference: https://chem.libretexts.org/Courses/Oregon_Tech_PortlandMetro_Campus/OT_-_PDX_-_Metro%3A_General_Chemistry_I/03%3A_Nuclei_Ions_and_the_Periodic_Table/3.03%3A_Predicting_Charges_of_Ions

Determining the Formula of Ionic Compound with Metal has Multiple positive charges from a Name and Determining Its name from the Formula

Figure 7.22 Nomenclature of Ionic compound( Transition metal)

Reference: https://chem.libretexts.org/Courses/College_of_Marin/CHEM_114%3A_Introductory_Chemistry/05%3A_Molecules_and_Compounds/5.07%3A_Naming_Ionic_Compounds

Some metal ions have multiple charges. The periodic table shows some metals with their multiple charges.

To name the ionic compound or to write the correct ionic formula, one has to use the Roman Numbers to distinguish the different charges of the metal cation

For example:

Iron-III-chloride is written as a formula as:

Fe ³⁺  and Cl  ^–. Swap the values of the charges only not the sign, then one obtains Fe ₁ Cl ₃.

The ionic compound will be FeCl₃. The value of 1 is understood but it is not written.

FeCl₃ is named as Iron -III-Chloride. Note that the subscript of 3 means came from Fe and hence Fe has to have 3 positive charges.

The same approach on can name and obtain the formula of Iron-II-chloride as shown in the figure above.

Reference: 

Transfer of Electrons In Ionic Bonding

Reference: Formation of Ionic Compounds