Question

The correct order of density of the following elements is: (Be, Mg, Ca, Sr)
A. Be> Mg > Ca> Cr
B. Ca> Mg > Be > Sr
C. Ca < Mg < Be < Sr
D. Mg < Ca < Sr < Be

Answer 1

Hint: Periodic table is a great source of information about the elements and their relation to each other. Changes of different periodic properties. Also, this helps to predict the properties of the elements even if they are not discovered. Be, Mg, Ca, Sr are from group II. Which is on the left side of the periodic table.

Complete step by step answer:
To answer this question the periodic properties of the elements from the different groups should be known. The elements in periodic tables are arranged in a way that every element of each group shows similar physical characteristics and chemical characteristics. But due to some opposite trends of periodic properties from left-right and top-bottom, there are some similarities observed between two different group elements.
In the periodic table, all the elements are arranged by the atomic numbers. Generally, on the left side of the periodic table, elements are metallic in nature. Moving from left to right the metallic character decreases and the non-metallic character increases. At the extreme right elements are non-metallic in nature.
In the case of Be, Mg, Ca, Sr group II elements, the force of attraction depends on the size of the element. With the increasing size of the element volume of the atom increases therefore the density decreases. Now, for the bottom elements, the molecular mass is very high compared to its volume, and also due to the strong attraction force, the density increases.
So, the order of density is down the group at first decreases then increases.
The order is, Ca < Mg < Be < Sr
The correct answer is, C

Note:According to periodic properties of the elements of the second period (Li, B, Be) and third period (Mg, Al, Si) elements which are diagonally present with each other in the periodic table, show some similar kind of chemical properties. For example, the formation of nitrides, halides. This kind of similarity of their properties is called diagonal relationship. Due to this, the chemistry of lithium is very similar to that of magnesium even though they are placed in different groups.