MediumChemistryHigh School (9–10)GeneralThe Periodic Table › Development of the Periodic TableNumericalBoard Exam
The periods of the modern table hold 2, 8, 8, 18, 18, 32 and 32 elements…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
The periods of the modern table hold , , , , , and elements. What is the atomic number of the last element of period ? Which group is it in, and which family?
Need a reminder? The key ideaShow
The modern table is ordered by atomic number: groups and periods holding , , , , , and elements. The period is the number of shells. Groups 1 and 2: group outer electrons. Groups 13 to 18: group outer electrons.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Add the periods. .
Step 2. Its place. The last element of a period ends the row, in group .
Answer: atomic number , in group 18: a noble gas, radon.
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