Question

Analyze how atomic radius changes with atomic number. Please provide evidence using the elements sodium (Na), aluminum (Al), phosphorus (P), and potassium (K) to support your claim.

Answer 1

The atomic radius generally decreases across a period and increases down a group. Sodium, aluminum, phosphorus, and potassium provide evidence for this trend.

Step-by-step explanation:

The atomic radius is a measure of the size of an atom, specifically the distance from the nucleus to the outermost electron shell. When we look at the periodic table and analyze how atomic radius changes with atomic number, we can observe a clear trend. The atomic radius generally decreases across a period from left to right and increases down a group. Let's take the elements sodium (Na), aluminum (Al), phosphorus (P), and potassium (K) as examples.

1. Sodium (Na) has an atomic number of 11 and is located in period 3 and group 1. It has an atomic radius of 0.186 picometers (pm).
2. Aluminum (Al) has an atomic number of 13 and is also located in period 3 but in group 13. It has a slightly smaller atomic radius of 0.143 pm compared to sodium.
3. Phosphorus (P) has an atomic number of 15 and is located in period 3 and group 15. It has a smaller atomic radius of 0.110 pm compared to aluminum.
4. Potassium (K) has an atomic number of 19 and is located in period 4 and group 1. It has a larger atomic radius of 0.231 pm compared to sodium.

From these examples, we can see that as we move from sodium to aluminum to phosphorus, the atomic radius generally decreases. However, when we compare potassium to sodium, we see an increase in atomic radius.

Therefore, based on the evidence from sodium, aluminum, phosphorus, and potassium, we can conclude that as the atomic number increases across a period, the atomic radius generally decreases, and as the atomic number increases down a group, the atomic radius generally increases.