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Why do first ionisation energies decrease down a group but increase across a period?

The nucleus contains positively charged protons which attract the negative electrons, the first ionisation energy is the energy required to overcome this attraction and remove 1 electron As you go down a gro...
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Answered by Amy M. • Chemistry tutor
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What does Le Chatelier's principle say happens to an equilibrium when temperature is changed or a catalyst is added?

The temperature moves the equilibrium differently depending on if the forwards reaction is exothermic or endothermic. If its endothermic the equilibrium moves to the right giving more products. The addition ...
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State and explain the trend in boiling points of chlorine, bromine, and iodine

Boiling point increases down the group, because of increasing strength of van der Waals (intermolecular) forces. More energy is required to break van der Waals (intermolecular) forces.Follow up questions cou...
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What is the definition of a H-Bond?

A H-bond is an attraction between molecules. It is therefore an intermolecular force, and in fact one of the strongest. Molecules which exhibit H-bonding must contain a hydrogen that is directly bonded to a ...
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Answered by Oliver M. • Chemistry tutor
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Why does Phosphorus have a higher melting point than Chlorine?

Phosphorus exists as P 4 and chlorine as Cl 2 so elemental phosphorus is a bigger molecule than chlorine. Neither of these molecules has a dipole so both have only induced dipole-dipole (or Van Der Waal's) f...
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Answered by Rory S. • Chemistry tutor
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