Question

question 6. select all the elements that have a smaller atomic radius than sodium (na).
□ magnesium (mg)
□ aluminum (al)
□ potassium (k)
□ neon (ne)
□ barium (ba)

Explanation:

To determine which elements have a smaller atomic radius than sodium (Na), we use the periodic trends of atomic radius:

• Across a period (left to right): Atomic radius decreases because the number of protons increases, pulling electrons closer to the nucleus.
• Down a group (top to bottom): Atomic radius increases because additional electron shells are added.

Step 1: Analyze Magnesium (Mg)

Magnesium is in the same period (period 3) as sodium but to the right of sodium. As we move right across a period, atomic radius decreases. So, Mg has a smaller atomic radius than Na.

Step 2: Analyze Aluminum (Al)

Aluminum is also in period 3, to the right of magnesium (and thus further right than sodium). Following the period trend, Al has a smaller atomic radius than Na.

Step 3: Analyze Potassium (K)

Potassium is in the same group (group 1) as sodium but below sodium. As we move down a group, atomic radius increases. So, K has a larger atomic radius than Na.

Step 4: Analyze Neon (Ne)

Neon is in period 2, while sodium is in period 3. Neon has one fewer electron shell than sodium. Also, neon is a noble gas with a stable electron configuration, and its atomic radius is smaller than that of elements in the next period (like Na) due to fewer electron shells and effective nuclear charge. So, Ne has a smaller atomic radius than Na.

Step 5: Analyze Barium (Ba)

Barium is in group 2, far below sodium (in period 6, while Na is in period 3). Moving down a group increases atomic radius, so Ba has a larger atomic radius than Na.

Answer:

The elements with a smaller atomic radius than sodium (Na) are:

• Magnesium (Mg)
• Aluminum (Al)
• Neon (Ne)