Covalent Bonding & Coordinate (Dative Covalent) Bonding (CIE A Level Chemistry)

Phosphorus reacts with chlorine to form PCl₅.

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PCl₅ is an example of a compound that exists as two structures depending on the conditions.

2PCl₅ (g) [PCl₄]⁺[PCl₆]^– (s)

Draw diagrams to suggest the shapes of [PCl₄]⁺ and [PCl₆]^–.

A student suggests that the PCl₅ molecule has sp³ hybridisation. Explain why the student is not correct.

Antimony(V) chloride is another Group 15 chloride. Under standard conditions, it is a liquid made from SbCl₅ molecules.

Explain why phosphorus(V) chloride in its solid form has a higher melting point than antimony(V) chloride.

Under the right conditions, molecules of SbCl₅ join together to form Sb₂Cl₁₀.

Complete Fig. 4.1 to show the bonding in Sb₂Cl₁₀.

The other Group 15 elements also form pentachlorides with the exception of nitrogen.

Suggest a reason why nitrogen does not form NCl₅.

Alkenes contain a carbon to carbon double bond that consists of a σ bond and a π bond.

Complete the diagram to show the areas of electron density for each bond.
Label the σ bond and the π bond.

Use the information in Table 5.1 to explain why ethene contains stronger covalent bonds between carbons atoms than ethane.   

Table 5.1.

Bond length and bond energies can be used to compare the reactivity of covalent molecules. 

Compare the reactivity of hydrogen halides using the information in Table 5.2.

Table 5.2

The boiling points of the hydrogen halides are shown in Table 5.3.