Recall Sem 1: Electrons in Atoms

The position of the element in Periodic Table that has an electronic configuration of 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p³.

• Group 13 Period 3

• Group 13 Period 4

• Group 15 Period 3

• Group 15 Period 4

Al and Cr³⁺ have the same number of unpaired electrons.

• TRUE

• FALSE

A 3p orbital can hold a maximum of 6 electrons.

• TRUE

• FALSE

Which terms cannot be illustrated by an equation that includes the formation of a positive ion?

• First ionisation energy

• Heterolytic fission of a covalent bond

• Enthalpy change of atomisation

• Dissociation of an acid

Why is the first ionisation energy of oxygen less than that of nitrogen?

• The electron removed is further away from nucleus in oxygen atom.

• Greater nuclear charge on oxygen atom.

• Oxygen atom has a pair of electrons in one p orbital.

• There is more shielding in oxygen atom.

The relative first ionisation energies of four elements with consecutive atomic numbers below 20 are shown on the graph. One of the elements reacts with hydrogen to form a covalent compound with formula HY.

Which element could be Y?

• A

• B

• C

• D