1. Based on the periodic trends for metallic properties, which elements have the biggest atomic radius?
2. Sort the elements in order of increasing metallic properties: Ca, Mg, Sc, Be, Ba.
3. Why is the electronegativity value of most noble gases zero?
4. A nonmetal has a smaller ionic radius compared with a metal of the same period. Do you agree?

1. Based on the periodic trends for metallic properties, which elements have the biggest atomic radius?

The biggest atomic radius is found in elements located toward the bottom-left corner of the periodic table. Atomic radius increases when moving down a group because atoms gain more electron shells, and it increases when moving left across a period because the nucleus attracts the electrons less strongly.

Therefore, among the elements in general, elements such as cesium (Cs) and francium (Fr) have some of the largest atomic radii. In a given group, the element lower down has the larger radius.

2. Sort the elements in order of increasing metallic properties: Ca, Mg, Sc, Be, Ba.

Metallic properties increase down a group and from right to left across a period.

The elements are:

• Be (beryllium) — Group 2, Period 2

• Mg (magnesium) — Group 2, Period 3

• Ca (calcium) — Group 2, Period 4

• Ba (barium) — Group 2, Period 6

• Sc (scandium) — Group 3, Period 4

For increasing metallic properties (least metallic to most metallic):

Be < Mg < Sc < Ca < Ba

Beryllium is the least metallic because it is higher on the periodic table, while barium is the most metallic because it is farther down Group 2.

3. Why is the electronegativity value of most noble gases zero?

Most noble gases have an electronegativity value of zero because their outer electron shells are already completely filled. They are very stable and usually do not need to gain or share electrons with other atoms.

Since electronegativity measures how strongly an atom attracts bonding electrons, noble gases generally do not attract additional electrons, so their electronegativity is considered zero or nearly zero.

4. A nonmetal has a smaller ionic radius compared with a metal of the same period. Do you agree?

Yes, I agree.

In the same period, metals usually form positive ions (cations) by losing electrons. Losing electrons reduces electron-electron repulsion and often makes the ion smaller than the original atom.

Nonmetals usually form negative ions (anions) by gaining electrons. However, when comparing a metal ion and a nonmetal ion from the same period, the metal ion is often smaller because it has fewer electrons and a stronger effective nuclear attraction on the remaining electrons.

For example, in Period 3:

• Na⁺ (metal ion) is very small because sodium loses an electron.

• Cl⁻ (nonmetal ion) is larger because chlorine gains an electron.

So the statement is not always correct if comparing ions, because nonmetal ions are often larger than metal ions. But if comparing neutral atoms, nonmetals generally have smaller atomic radii than metals in the same period.