The heavier noble gases do have a full d-shell as well.

You can fill four successive s orbitals before a d-shell configuration becomes energetically favorable, so there is no d-shell for Helium, Neon, and Argon.

Krypton has a filled d-orbital. Helium only has a full 1s, no p or d.

But isnt the dshell part of the valence shell of that energy level? I know you skip to the s sublevel of the next level before going back to d. Does this mean the level is not a part of the valence shell for that particular level?

There is no 1p, 1d, or 2d structure. These atoms are too small and compact to support the more complex and diffuse electron configurations required to stuff dozens of them into the same space.

The 3d does exist, but it’s higher energy than the 3p and 4s and so doesn’t fill in until later.

Eventually you’ll fill an f-orbital too.

I know this, im just wondering if d is a part of the valence shell of that energy level. People say that noble gases have full valence shells but us ut really full if d sublevel is skipped?

For the 3rd level the noble gas only full s and p levels, skipping d sublevel so the valence shell is not truely full for noble gases past argon right?

The notion of "shells" is a simplification.

You are familiar, I imagine, with the idea of the s-, p-, d-, and f-orbitals, since you mention them in your post. These correspond to ℓ = 0, 1, 2, and 3 respectively in the state of an electron. And they come in different levels, given by the value of n, also part of the description of an electron. So for example, the 2s subshell corresponds to n = 2 and ℓ = 0.

As a broad rule, these subshells are filled in the following order:

• Subshells with lower n + ℓ are filled first.
• For subshells with the same n + ℓ, start with the lowest n.

That results in the order 1s, 2s, 2p, 3s, 3p for the first three rows (with n+ℓ values of 1, 2, 3, 3, 4, 4 respectively). But once you get to the next row, the first that contains d electrons, it goes 4s, 3d, 4p. It doesn't "skip" d, it's just that the d it's filling in the fourth row of the periodic table is the 3d subshell, not the 4d one. The noble gas in that row (krypton, as it happens) does in fact have its highest occupied d shell filled. It has the electron configuration [Ar] 4s^(2) 3d^(10) 4p^(6) - this 3d subshell is full.

The reason the 3d shell shows up between 4s and 4p here, even though the n is nominally an energy level, is that that these numbers describe the energies of an orbital in the absence of other electrons. But other electrons in the atom jostle energy levels quite a bit. It turns out that when lower orbitals are occupied, d- orbitals end up so high energy that they effectively get "bumped up a tier" of the table.

It doesn't have any 4d electrons yet, because 4d electrons would be much higher energy than the 4s, 3d, and 4p electrons it actually has.

The better way to think about this is in terms of the gaps in energy levels. Noble gases have a large gap between the energy level of the highest-energy electron they have and the next available electron slot. That makes sticking an electron to them hard, because that electron has to occupy a high-energy state. And it makes stripping an electron off of them hard too, because all the electrons they have occupy low energy states. Their configurations look like this (where the blue lines represent energy of occupied orbitals, and red represents unoccupied orbitals).

As you go down the periodic table, the notion of "shells" starts to become less useful, because the gaps between the shells shrinks enough that the gaps within the shells can start to cause them to spill over one another. So chemistry near the bottom of the periodic table becomes more complicated, and in fact it's generally believed that if element 118 - which is one of the noble gases by its position on the periodic table - would actually be a solid if it were stable enough to stick around and have any chemistry at all.

> I know this, im just wondering if d is a part of the valence shell of that energy level.

The 3d shell is on the same level as the 3s and 3p orbitals in a hydrogen atom, but in the larger atoms that actually fill the 3d shell in their ground state, it turns out that the 3d shell ends up much higher-energy than the 3s and 3p shells because of how it interacts with other electrons. It ends up with an energy between the 4s and 4p orbitals instead, so for the purposes of the periodic table, you can think of 3d as hanging out in the fourth "shell" instead.

“Valence” refers to the highest level of orbital(s) where electrons relatively freely wander between structures with similar energy levels. How many electrons this is will vary with atomic size.

1s is the lowest orbital, and has no friends - so helium’s valence shell is just two electrons.

Then there’s a big jump.

2s is similar in energy to 2p, and so electrons will move between the two. To fill this next valence layer you need eight electrons.

Then there’s a big jump

3s is similar to 3p, again giving you an 8-valence level.

Then there’s a big jump.

4s is where you’re now at energy levels high enough to generate a d-orbital, and 4s, 3d, and 4p form all sorts of wacky structures. This layer has 18 in the valence level.

Then… you guessed it… there’s a big jump.

“Full valence” is where these big jumps occur. Adding or subtracting an electron from a full structure is relatively difficult. You’re either forming an entirely new structure on top of the existing one or destabilizing a fully spin-paired configuration. Both are difficult, and so atoms and ions with full valence are highly chemically stable.

Which is why the transition metals start in the fourth period, but utilize the 3d orbital