A tabular arrangement of elements in groups and periods that highlights the regular trends in properties of elements is defined as the periodic table.
Number of elements in a period
- The first period contains only two elements 1H and 2He and is known as the shortest period.
- The second period (3Li to 10Ne) and the third period (11Na to 18Ar) contain 8 elements each and are known as short periods.
- The fourth period (19K to 36Kr) and the fifth period (37Rb to 54Xe) contains 18 elements each and are called long periods.
- The sixth period contains 32 elements (55Cs and 86Rn) and is also known as the longest period.
- The seventh period is an incomplete period.
Groups in the modern periodic table
There are eighteen vertical columns known as groups in the modern periodic table which are arranged from left to right and seven horizontal rows which are known as periods.
|roup number||Group name||Property|
|Group 1 or IA||Alkali metals||They form strong alkalis with water|
|Group 2 or IIA||Alkaline earth metals||They also form alkalis but are weaker than group 1 elements|
|Group 13 or IIIA||Boron family||Boron is the first member of this family|
|Group 14 or IVA||Carbon family||Carbon is the first member of this property|
|Group 15 or VA||Nitrogen family||This group has non-metals and metalloids|
|Group 16 or VIA||Oxygen family||They are also known as chalcogens|
|Group 17 or VIIA||Halogen family||The elements of this group form salts.|
|Group 18||Zero group||They are noble gases and under normal conditions they are inert.|