Atomic structure and the Periodic Table — Chemistry 5070 O Level Question & Worked Solution

In the Periodic Table, the elements are organised into groups and periods. Which row is correct?

Agroup: number of electrons in the outer shell | period: number of occupied shells | arranged by increasing proton number
Bgroup: number of occupied shells | period: number of electrons in the outer shell | arranged by increasing mass number
Cgroup: number of electrons in the outer shell | period: number of occupied shells | arranged by increasing mass number
Dgroup: number of occupied shells | period: number of electrons in the outer shell | arranged by increasing proton number

Atomic structure and the Periodic Table — practice question