What is common about the elements of a period? select all that apply. they have the same number of electron energy levels. they have similar chemical characteristics. they have similar physical characteristics. they transition from a metal to noble gas.

The correct statements are they have the same number of electron energy levels and they transition from a metal to noble gas.

Explanation:

Elements are arranged in 7 periods and 18 groups in a periodic table.

Elements that are arranged in same group have same number of valence electrons and hence show similar chemical properties.

Elements that are arranged in same period have same number of energy levels. In a periods, first metals come, then non-metals and a period ends with a noble gas always.

Hence, the correct statements are they have the same number of electron energy levels and they transition from a metal to noble gas.

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explanation:

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