Questions: Which of the following correctly describes the elements in the same group of the periodic table? The number of electrons in their valence shell does not change as one moves down the group. The atomic radius of these elements does not change as one moves down the group. The atomic radius of these elements decreases as one moves down the group. The number of electrons in their valence shell increases as one moves down the group.

Analyzing the characteristics of elements in the same group of the periodic table.

Valence electrons in a group

Elements in the same group of the periodic table have the same number of electrons in their valence shell. This is because elements in a group share similar chemical properties, which are largely determined by the number of valence electrons. Therefore, as one moves down a group, the number of valence electrons remains constant.

Atomic radius trend in a group

As one moves down a group in the periodic table, the atomic radius of the elements increases. This is because each successive element has an additional electron shell, which increases the distance between the outermost electrons and the nucleus, resulting in a larger atomic radius.

\(\boxed{\text{The number of electrons in their valence shell does not change as one moves down the group.}}\)

\(\boxed{\text{The number of electrons in their valence shell does not change as one moves down the group.}}\)
The correct description of elements in the same group is that the number of electrons in their valence shell does not change as one moves down the group.