Which of the following elements has the smallest atomic radius? Be, Mg, Ca, Sr, Ba, or Ra
The correct answer and explanation is:
The element with the smallest atomic radius is Be (Beryllium).
The atomic radius of an element refers to the distance from the nucleus to the outermost electron in a neutral atom. As you move down a group in the periodic table, the atomic radius increases due to the addition of electron shells. This results in the outermost electrons being farther from the nucleus. On the other hand, across a period (from left to right), the atomic radius decreases because electrons are added to the same shell, but protons are also being added to the nucleus. This increases the nuclear charge, attracting the electrons more strongly and pulling them closer to the nucleus.
Looking at the given elements:
- Be (Beryllium) is in Group 2 of the periodic table and is the first element in this group. It has the smallest atomic radius because it is the farthest to the right in its period and is in the second period. The increased nuclear charge pulls the electrons closer to the nucleus.
- Mg (Magnesium), Ca (Calcium), Sr (Strontium), Ba (Barium), and Ra (Radium) all belong to the same group as Be, but they are located further down. As you go down the group, the number of electron shells increases, causing the atomic radius to grow.
Thus, Be has the smallest atomic radius because it is located in the second period, where there are fewer electron shells compared to the others. Additionally, the increased nuclear charge in Be pulls its electrons closer to the nucleus, resulting in a smaller atomic radius than the elements further down the group.