Ionic Bonding

How are ions are formed by electron loss or gain?

How are ions are formed by electron loss or gain?

Ions are electrically charged particles formed when atoms lose or gain electrons. (get a full outer shell)

Metal atoms form positive ions (cations).

 

 

 

Non-metal atoms form negative ions (anions).

What are the charges of these ions:

• metals in Groups 1, 2 and 3

• non-metals in Groups 5, 6 and 7

• Ag, Cu, Fe, Fe, Pb, Zn

• hydrogen (H), hydroxide (OH), ammonium (NH4), carbonate (CO3), nitrate (NO3), sulfate (SO4).

When given this information of the following ions, it is possible to work out the formulae of ionic compounds which include these ions.

Name of Ion	Formula	Charge
Sulfate	SO42-	-2
Carbonate	CO32-	-2
Nitrate	NO3-	-1
Hydroxide	OH-	-1
Ammonium	NH4+	+1
Silver ion	Ag+	+1
Zinc ion	Zn2+	+2
Hydrogen ion	H+	+1
Copper (II) ion	Cu2+	+2
Iron (II) ion	Fe2+	+2
Iron (III) ion	Fe3+	+3
Lead (II) ion	Pb2+	+2

Ion charges on the periodic table

How do you write formulae for compounds formed between the ions listed before?

IONIC COMPOUNDS: Formed when Atoms of Metals transfer Electrons to atoms of Non - Metals to form Compounds made up of ions

FORMULAE FOR COMPOUNDS FORMED BETWEEN IONS

• METALS: Loses Electrons to another atom and become Positively Charged Ions

• NON - METALS: Gains Electrons from another atom to become Negatively Charged Ions

Example 1:

Sodium Chloride, NaCl (typical Ionic Bond)

SODIUM ATOM Sodium is a Group 1 Metal so will need to lose one outer Electron to another Atom to have a full outer shell of Electrons They will lose an Electron to form a Positive ion with the Charge 1+ (as they lose one outer electron)           Na   2 . 8 . 1      →      Na+   2 . 8 CHLORINE ATOM Chlorine is a Group 7 Non-Metal so will need to gain an Electron to have a full outer shell of Electrons One Electron will be transferred from the outer shell of the Sodium atom to the outer shell of the Chlorine atom Chlorine atom will gain an Electron to form a Negative ion with Charge 1- (as they gain an outer electron)           Cl   2 . 8 . 7      →      Cl-   2 . 8 . 8 FORMULAE OF IONIC COMPOUND:    NaCl

Example 2:

Magnesium Oxide, MgO (typical Ionic Bond)

MAGNESIUM ATOM Magnesium is a Group 2 Metal so will need to lose two outer Electrons to another atom to have a full outer shell of Electrons They will lose two Electrons to form a Positive Ion with the Charge 2+ (as they lose two outer electrons)           Mg   2 . 8 . 2      →      Mg2+   2 . 8 OXYGEN ATOM Oxygen is a Group 6 Non-Metal so will need to gain two Electrons to have a full outer shell of Electrons Two Electrons will be transferred from the outer shell of the Magnesium atom to the outer shell of the Oxygen atom Oxygen atom will gain two Electrons to form a Negative ion with Charge 2- (as they gain two outer electrons)           O2   2 . 8 . 6      →      O22-   2 . 8 . 8 FORMULAE OF IONIC COMPOUND:    MgO

How do you draw dot-and-cross diagrams to show the formation of ionic compounds by electron transfer, limited to combinations of elements from Groups 1, 2, 3 and 5, 6, 7?

(only outer electrons need be shown)

Sodium chloride, NaCl

 

  

Magnesium chloride, MgCl₂

 

Potassium oxide, K₂O

 

Calcium oxide, CaO

 

Aluminium oxide, Al₂O₃

 

 

Magnesium nitride, Mg₃N₂

How can we comprehend ionic bonding through the lens of electrostatic attractions?

Ionic Bonds

• As a general rule, metals are on the left of the periodic table and nonmetals are on the right-hand side

• Ionic bonding involves the transfer of electrons from a metallic element to a non-metallic element

• Transferring electrons usually leaves the metal and the non-metal with a full outer shell

• Metals lose electrons from their valence shell forming positively charged cations

• Non-metal atoms gain electrons forming negatively charged anions

• Once the atoms become ions, their electronic configurations are the same as a noble gas

  • A potassium ion (K⁺) has the same electronic configuration as argon: [2,8,8]⁺

  • A chloride ion (Cl^-) also has the same electronic configuration as argon: [2,8,8]^-

Forming cations by the removal of electrons from metals

Forming anions by the addition of electrons to nonmetals

• Cations and anions are oppositely charged and therefore attracted to each other

• Electrostatic attractions are formed between the oppositely charged ions to form ionic compounds

• The ionic bond is the electrostatic attraction formed between the oppositely charged ions, which occurs in all directions ( this called non-directional bonding)

• This form of attraction is very strong and requires a lot of energy to overcome

  • This causes high melting points in ionic compounds

 

Cations and anions bond together using strong electrostatic forces, which require a lot of energy to overcome

• The ions form a lattice structure which is an evenly distributed crystalline structure

• Ions in a lattice are arranged in a regular repeating pattern so that positive charges cancel out negative charges

• The attraction between the cations and anions is occurring in all directions

  • Each ion is attracted to all of the oppositely charged ions around it

• Therefore the final lattice is overall electrically neutral

 

Ionic solids are arranged in lattice structures

Why do compounds with giant ionic lattices have high melting and boiling points?

Ionic compounds have high melting and boiling points because they have a giant structure with strong electrostatic forces between oppositely charged ions that require a lot of energy to break.

 

Giant 3D lattice of sodium chloride (NaCl)

When do ionic compounds conduct electricity?

Ionic compounds do not conduct electricity when solid.

However, ionic compounds do conduct electricity if molten or in solution.