Question

10. Name the factor that determines which element will
be the first and which the last in a period of the
periodic table.​

Answer 1

Explanation:

Element having one valence electron will be the first in period, element with valence electrons 8 in outermost shell comes last in a period except in first period where the last element has only 2 electron in outermost shell

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Answer 2

The number of shells in an element determines the elements which should be placed first and last in a period.