chem - bonding basics

Why does having more outer electrons generally give a higher melting point?

More outer electrons → more delocalised electrons → stronger attraction between the positive metal ions and delocalised electrons → stronger metallic bonding → more energy needed to break the bonds → higher melting point.

When does ionic bonding occur

Ionic bonding occurs when the outer electrons of a metal are transferred to the outer electron shell of a non metal.

Why does ionic bonding occur

They do this to complete their outer shells and become stable. This creates positive metal ions and negative non metal ions which are held together by a strong electrostatic attraction.

Why do atoms form bonds?

Atoms form bonds to become more stable by achieving a full outer electron shell. This happens by gaining, losing or sharing electrons.

How does electron transfer occur in ionic bonding?

• A metal atom loses its outer electron(s).

• A non-metal atom gains those electron(s).

• The metal becomes a positive ion (cation).

• The non-metal becomes a negative ion (anion).

• The oppositely charged ions attract, forming an ionic bond.

How are positive ions formed?

A positive ion is formed when an atom loses one or more electrons.

• Electrons have a negative charge.

• Losing negative electrons leaves the atom with an overall positive charge.

• Metals usually form positive ions.

How are negative ions formed?

A negative ion is formed when an atom gains one or more electrons.

• Electrons have a negative charge.

• Gaining negative electrons gives the atom an overall negative charge.

• Non-metals usually form negative ions.

What is ionic bonding?

Ionic bonding is the strong electrostatic attraction between oppositely charged ions.

What is the structure of a giant ionic lattice?

A giant ionic lattice is a regular, repeating 3D arrangement of positive and negative ions.

• Positive and negative ions alternate in a regular pattern.

• Each ion is surrounded by ions of the opposite charge.

• The ions are held together by strong electrostatic attractions in all directions.

• There are no individual molecules — it is one giant structure.

What particles carry electrical current in metals and ionic compounds?

Metals:
Delocalised electrons move and carry the charge.

Ionic compounds:
Ions move and carry the charge, but only when the compound is molten or dissolved.

Solid ionic compounds:
Ions are held in fixed positions, so they cannot conduct electricity.

Why do ionic compounds have high melting points?

Ionic compounds have strong electrostatic attractions between oppositely charged ions in their giant ionic lattice.

A large amount of energy is needed to overcome these attractions and separate the ions, so they have high melting points.

Why do ionic compounds conduct electricity when molten?

Molten → ions can move → charge is carried → conducts electricity.

Why do ionic compounds conduct electricity when dissolved in water?

Dissolved → ions separate → ions can move → carries charge → conducts electricity.

Why don’t solid ionic compounds conduct electricity?

In a solid ionic compound, the ions are held in fixed positions in the giant ionic lattice.

They cannot move, so they cannot carry electrical charge.