Use the drop-down menus to complete each sentence.
elements in the same have the same number of valence electrons.
elements in the same have the same number of electron shells.
metallic elements become reactive as you move left to right in a period.
metallic elements become reactive as you move top to bottom in a group.

Explanation:

Elements that belong to same group contains same number of valence electrons. Hence, they tend to show similar chemical properties.

When we move across a period then number of electrons get added to the same shell. As a result, there will be no increase in size of elements.

Also, metals are the elements that belong to group 1, 2 and d-block elements are also known as metals. Metallic character of elements decreases when we move left to right in a periodic table.

As most reactive metals are placed on the left side of periodic table.

Since, size of elements increases on moving down the group. So, an element is able to easily lose its valence electrons because of less force of attraction between its nucleus and valence electrons.

As a result, there will be increase in reactivity of metals on moving down the group.

Thus, we can conclude that given sentences are as follows.