Atomic radius - core charge vs energy level

In summary, the core charge is the most important factor in determining the size of an atom. For example, Berylium has a smaller radius than Lithium due to its greater core charge. However, in the case of Nitrogen vs Berylium, Nitrogen has a greater core charge but its electrons are in the 2p subshell, while Berylium only goes up to the 2s subshell. This can also be observed in the radial probability plots for hydrogen-like states, where the maximum probability for a 2p state is not at a higher radius value than the 2s state. However, it should be noted that these plots are not completely accurate for larger atoms.
  • #1
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which one is more important in determining the size of an atom?

for example - Berilium has a smaller radius than Lithium because it has a greater core charge, but what about Nitrogen vs Berilium? Nitrogen has a greater core charge, but it has electrons in the 2p subshell whereas Berilium only goes to 2s.

Thanks in advance
 
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  • #2
Hi ...,

Nitrogen has smaller radius than Berylium because of the core charge.

Hidrogen-like radial wavefunctions, although not valid for this case, can be used to qualitaively examine the behaviour of the radius (only in this little atoms, be carefull with this). If you look at the radial probability of a 2p state the maximum is not at higher radius value than the 2s, they are similar.

This is a 2s hidrogen-like radial probability graphic (for Z=4) and the corresponding contour plot in the xy plane, and the 2p plot for Z=7. Look at the maximums of prob. but don´t forget theese are hidrogen-like functions
 

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  • #3
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Both core charge and energy level play a role in determining the size of an atom. However, energy level is generally considered more important because it determines the distance of the outermost electrons from the nucleus. The higher the energy level, the further away the outermost electrons are from the nucleus, resulting in a larger atomic radius.

In the example of Beryllium and Lithium, Beryllium has a smaller radius because it has a greater core charge. This means that the positively charged nucleus is able to pull the outermost electrons closer to itself, resulting in a smaller atomic radius. However, in the case of Nitrogen and Beryllium, Nitrogen has a greater core charge but its outermost electrons are in the 2p subshell, which is further away from the nucleus compared to Beryllium's 2s subshell. This results in Nitrogen having a larger atomic radius despite having a greater core charge.

Overall, energy level is a more important factor in determining the size of an atom, as it directly affects the distance of the outermost electrons from the nucleus. Core charge may have an impact, but it is not the sole determining factor in atomic radius.
 

1. What is atomic radius?

Atomic radius is the distance from the center of an atom to its outermost electron shell. It is typically measured in picometers (pm) or angstroms (Å).

2. How does core charge affect atomic radius?

Core charge is the positive charge of an atom's nucleus. As the core charge increases, the attraction between the nucleus and the outermost electrons also increases, resulting in a smaller atomic radius.

3. What is the relationship between atomic radius and energy level?

As the energy level of an atom increases, the atomic radius also increases. This is due to the fact that higher energy levels have more orbitals and therefore more space for the electrons to occupy.

4. How does the periodic table reflect the trend of atomic radius?

The periodic table follows a general trend where atomic radius decreases from left to right across a period and increases from top to bottom down a group. This is due to the increasing number of protons and electrons, as well as the increasing energy levels.

5. Why do noble gases have the largest atomic radii in their respective periods?

Noble gases have a full valence shell, meaning they have the maximum number of electrons in their outermost energy level. This results in a larger atomic radius compared to other elements in the same period that have not yet achieved a full valence shell.

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