# Comparing Atomic Radii: K+ vs Ar

• rdgt3000
In summary, the atomic radius is a measure of the size of an atom, with the distance from the nucleus to the outermost electron orbit being the determining factor. The atomic radius of K+ is smaller than that of Ar due to the loss of an electron and stronger nuclear charge. As you move across a period in the periodic table, the atomic radius decreases, while it increases as you move down a group. This is due to the increased number of protons and electrons, and electron shells, respectively.
rdgt3000
which atom has a larger atomic radius: K+ or Ar ?

Both have the same number of electrons, but think about the number of protons in the nucleus of the K+ ion and in the Argon atom. How will the number of protons affect the atomic (or ionic) radius? Think of the general periodic trend of atomic radii when the outermost shell is the same but atomic number is increasing.

In general, atoms with more protons in their nucleus tend to have smaller atomic radii due to increased nuclear charge. Therefore, based on their atomic structures, it can be predicted that Ar, with 18 protons, will have a smaller atomic radius than K+, with 19 protons. This is because the additional proton in K+ will increase its nuclear charge, pulling the electrons closer to the nucleus and decreasing its atomic radius. Additionally, K+ has lost an electron compared to the neutral atom K, further decreasing its atomic radius. Therefore, K+ has a smaller atomic radius than Ar. However, it is important to note that other factors such as electron configuration and atomic bonding can also affect atomic radii and further research would need to be done for a more precise comparison.

## 1. What is the definition of atomic radius?

The atomic radius is a measure of the size of an atom, typically defined as the distance from the center of the nucleus to the outermost electron orbit.

## 2. How does the atomic radius of K+ compare to that of Ar?

The atomic radius of K+ is smaller than that of Ar. This is because K+ has lost an electron and has a higher nuclear charge, resulting in a stronger attraction to the remaining electrons and a smaller size.

## 3. Why is the atomic radius of K+ smaller than that of Ar?

As mentioned, the loss of an electron in K+ leads to a higher nuclear charge and stronger attraction to the remaining electrons, causing the atom to shrink in size.

## 4. How does the trend in atomic radius change as you move across a period in the periodic table?

As you move across a period in the periodic table, the atomic radius generally decreases. This is because the number of protons and electrons increases, leading to a stronger attraction between the nucleus and the electrons, causing the atom to become smaller.

## 5. How does the trend in atomic radius change as you move down a group in the periodic table?

As you move down a group in the periodic table, the atomic radius generally increases. This is because the number of electron shells increases, leading to a greater distance between the nucleus and the outermost electrons, resulting in a larger atom.

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