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Design of the modern periodic table: groups, periods and transitional metals

Answer Text:
Design of the modern periodic table:
It has vertical columns called groups and horizontal rows called periods.
Groups:
- Are the vertical columns of a periodic table.
- Are eight in number; ad numbered in capital Roman numerals I all through to VIII.
Note: group VIII is also called group zero because the elements have little tendency to gain o lose electrons during chemical reactions
- Between group 2 and group 3 is a group of elements called the transition metals;
Periods:
- Are the horizontal rows in a periodic table.
- They are 8 in number in a modern periodic table.
Transition metals.
- Are elements that form a shallow rectangle between group II and group III.
- These elements are generally metallic and hence the name “transition metals”
- They are not fitted in any group because they have variable valencies.
- Are sometimes called the “d-block” elements.
Lanthanides and Actinides.
- They form a block of elements within the transition metals.
- Are sometimes called the inner transition metals.
- The lanthanides consist of 14 elements from Cerium (Ce) to Lutetium (Lu).
- The Actinides are the 14 elements from Thorium (Tho) to Lawrencium (Lr).