Question

All elements of a particuler period the electrons are gradually filled in shell?

Answer 1

Answer:

Group 1 contains alkali metals (Li, Na, K, Rb, Cs and Fr).

The alkaline earth metals are metallic elements found in the group 2 of the periodic table.  

Elements present in groups 3 to 12 in the middle of the periodic table are called transition elements. In the transition elements, valence electrons are present in more than one shell.

Group 18 on extreme right side position contains noble gases ( He, Ne, Ar, Kr, Xe and Rn ). Their outermost shell contains 8 electrons except He as its outermost shell is K shell and it can hold only 2 electrons.  

Inner transition elements:

14 elements with atomic numbers 58 to 71 (Ce to Lu) are called lanthanides  and they are placed along with the element lanthanum (La), atomic number 57 in the same position (group 3 in period 6) because of very close resemblance between them.

14 elements with atomic numbers 90 to 103 (Th to Lr) are called actinides and they are placed along with the element actinium (Ac), atomic number 89 in the same position (group 3 in period 7) because of very close resemblance between them.