What happen when moving top to …

• Position of Elements in the Periodic Table:

Periods:

The horizontal rows in the Modern Periodic Table are called periods.

The Modern Periodic Table consists of seven periods which are numbered from 1 to 7.

In each period, a new shell starts filling up. The period number is also the number of shell which starts filling up.

The  elements  in  a period  have  consecutive  atomic  numbers,  and  the  number  of  elements  in  each period is given below:

1. First period contains 2 elements and is called a very short period.
2. Second and third periods contain 8 elements and are called as short periods.
3. Fourth and fifth periods are long periods and contain 18 elements each.
4. Sixth period is the longest and contains 32 elements.
5. Seventh period is an incomplete period.

Characteristics:

1. The elements in a period have consecutive atomic numbers.
2. The no. of elements in period is fixed by the maximum no. of electrons which can be accommodated in various shells.

Groups:

1. The vertical columns are called groups and consist of eighteen groups numbered from 1 to 18.
2. Elements having the same number of valence electrons are present in the same group.
3. Elements present in the same group show the same chemical properties.
4. Group 1 contains alkali metals and these elements contain 1 electron in their outermost shell.
5. Group 2 contains alkaline earth metals and these elements contain 2 electrons in their outermost shell.
6. Groups 3 to 12 have their two outermost shells incomplete.
7. Groups 13 to 18 group contain 3 to 8 electrons in their outermost shell.
8. Group  18  elements  have  complete outermost  shells.  So  they  are  called  noble  elements  or  noble  gases.
9. The  element  hydrogen  has  been  placed  at  the  top  of  group  1 because its electronic configuration is similar to alkali metals.

Characteristics:

1. The elements in a group do not have consecutive atomic numbers.
2. All the elements in a group have similar electronic configurations and show similar properties.