Which of the given elements A,B,C,D and E with atomic number 2,3,7,10 and 30 respectively belong to the same period ?

Five elements A,B,C,D and E have atomic numbers of 2,3,7,10 and 18 respectively. The elements which belong to the same period of the periodic table are:

The elements A,B,C,D and E have atomic number 9,11,17,12 and 13 respectively. Which pair of elements belong to the same group?

The elements A, B, C, D and E have atomic number 9, 11, 17, 12 and 13 respectively. Which pair of elements belongs to the same group ?

What valencies will be shown by the elements A, B, C, D and E having atomic numbers 2, 4, 8, 10 and 13 respectively.

The atomic numbers of the three elements X,Y and Z are 2,6 and 10 respectively (i) Which two elements belong to the same group? (ii) Which two elements belong to the same period? Given reasons for your choice.

Which of the following elements shown as pairs with their atomic numbers belong to the same period?