1What are isotopes? Give an example.
2Why was atomic weight not a suitable basis for classifying elements?
3State the modern periodic law. Who gave it, and when?
4Differentiate between a group and a period.
5How many elements are there in each period of the modern periodic table? State the nature of each period.
6Name the families of elements found in groups IA, IIA, VIIA and 0.
7What are lanthanides and actinides? Why are they kept below the main table?
8Where are metals, non-metals and metalloids placed in the modern periodic table?
9What are transition metals? How many columns do they occupy?
10Find the period and group of the element with atomic number 19.
11What are the s, p, d and f blocks? Which part of the table does each cover?
12Why is it correct to keep the three isotopes of carbon in one box of the modern periodic table?