Dative, Ionic and Metallic Bonding

Co-ordinate Bond (Dative Bond)

A Co-ordinate bond is a covalent bond where both of the electrons in the bond come from just one of the atoms involved

Co-ordinate bond strength

Is the same as an equivalent covalent bond

Examples of a co-ordinate bond

Dot and cross diagram for a dative bond

Structural formula for a dative bond

Ions needed to learn

Ammonium

Nitrate

Sulfate

Carbonate

Hydrogen carbonate

Hydroxide

Hydride

Phosphate

Ionic bonding

Strong electrostatic attraction between oppositely charged ions arranged in a giant lattice.

Metallic bonding

Strong electrostatic attraction between a regular lattice of positive metal ions and a surrounding sea of delocalised electrons.

Number of positive charge in an ion dictates the number of _______ ______

Delocalised electrons

How does increasing nuclear charge across a period affect metallic bonding strength.

• Number of delocalised electrons per ion increases because the metal atoms have more outer-shell electrons.

• The ionic radius decreases because a higher nuclear charge pulls the electron shells in closer to the nucleus.

• The charge density increases due to the higher ionic charge and smaller ionic size.

• There is a stronger electrostatic attraction between the positive metal ions and the delocalised electrons.

• More energy is required to overcome these stronger metallic bonds, resulting in higher melting points.

How does strength of metallic bonding change down a period

• Number of delocalised electrons per ion remains the same at one electron per ion.

• The ionic radius increases down the group because there are more electron shells and more shielding.

• This means the delocalised electrons are further away from the positive metal ions.

• Therefore, there is a weaker electrostatic attraction between the positive metal ions and the delocalised electrons.

• Less energy is required to overcome these weaker metallic bonds, resulting in lower melting points.

Why is metallic bonding of magnesium is stronger than sodium.

• More Delocalised Electrons: Magnesium has twice as many delocalised electrons per ion due to 2+ charge compared to Na+

• Smaller Ionic Radius: Magnesium has a higher nuclear charge (12 protons vs 11), which pulls the remaining electron shells closer, making the Mg2+ ion smaller

• Higher Charge Density: Because the Mg2+ ion has a higher charge and a smaller size, it has a much higher charge density.

• Stronger Electrostatic Attraction: This results in a much stronger electrostatic attraction between the positive ions and the delocalised electrons.

• Higher Melting Point: Therefore, significantly more energy is required to break these stronger metallic bonds, resulting in a higher melting point