Question

Which of the following remains unchanged on descending a group in the periodic table?
A.Valence electron
B.Atomic size
C.Density
D.Metallic character

Answer 1

Hint:Modern periodic table states that the physical and chemical properties of an element of periodic function of its atomic number. There are 18 groups and 7 periods which are distributed in four blocks namely s, p, d and f. In the modern periodic table group number 1 to 2 in s block, group number 13 to 18 are in p block, group 3 to 12 are in the d block and 14 elements are in f block.

Complete step by step solution:
Generally elements in a group have similar outer shell electronic configuration. The general electronic configuration of the valence shell is the same for elements that belong to the same group. The electrons present in valence shells are known as valence electron.On moving down the group generally the valence shell electronic configuration remains the same. The atomic size, density and metallic character generally changes either we move in a period or in a group.
Valence shell is the outermost shell or we can say it is the last shell of any element in which electrons are filled. As we move down the group at each subsequent step one shell increases but still the number of electrons in the last shell remains constant. This is because the atomic number follows a specific Trend which repeats when elements fall under the same group.

Hence, the correct option is option A.

Note:
While atomic size, density and metallic character increases as we move down the group. This is because each new shell adds up while moving down the group and hence mass and density increases. Ionization energy decreases as we move down the group and hence metallic character of the element increases.