Lakhmir Singh & Manjit Kaur Test: Periodic Classification of Elements

At no. of elements a,b,c,d,e are 2,3,7,10,30. Elements b , c , d belongs to the same period because the no. of valence shells are all 2. Elements B (Li), C (N) and D (Ne) belong to the same group.

Atomic radii increases as you move left to right or down the columns of the periodic table. Within a period of elements, each new electron is added to the same shell. When an electron is added, a new proton is also added to the nucleus, which gives the nucleus a stronger positive charge and a greater nuclear attraction. So as more electrons are added, the total radius of the atom increases. And so out of all the options, potassium (K) has the largest atomic radii.

For the second period elements, L-shell is the outermost shell.

Moving from right to left the periodic table metallic character increases and if metallic character increase atomic size will also increase as a result atomic radii increase.

Group 18, the element is Neon. It belongs to group 18.

The greater the valency of the element, the greater is its unreactivity. Also, the valency in a period increases from the left to the middle, then again decreases from middle to the right. So we can say that the unreactive elements are located in the center of the period. Since phosphorus and Silicon are located at the center, they have the highest number of Valence electrons, and hence are the most unreactive in the period.

Modern periodic table has 18 vertical columns known as groups.

The group 16 elements of modern periodic table consist of 5 elements oxygen, sulphur, selenium, tellurium and polonium. The elements in this group are also known as the chalcogens. 

This is the correct order of increasing non-metallic character.

Trend of atomic size is :- 
In period it decreases due to large Electronegativity . In group it increases due to low  Electronegativity. According to this order, option ( b) is correct.