Period
What is Period?
In the periodic table, a period is a horizontal row of elements. All elements in the same period have the same number of electron shells. Moving left to right across a period, the atomic number increases by one, and the elements transition from metals to metalloids to non-metals. There are seven periods; the first is the shortest (2 elements) and the sixth and seventh are the longest (32 elements including lanthanides/actinides).
Key Facts
Frequently Asked Questions
In the periodic table, a period is a horizontal row of elements. All elements in the same period have the same number of electron shells. Moving left to right across a period, the atomic number increases by one, and the elements transition from metals to metalloids to non-metals. There are seven periods; the first is the shortest (2 elements) and the sixth and seventh are the longest (32 elements including lanthanides/actinides).