 So let's try to do these types of problems. So what is the number of inner electrons for this atom and what is the effective nuclear charge for it? So the number of inner electrons, that's going to equal the noble gas is plus the fill these plus the fill. So in order to do this, probably the best thing to do is write the electron configuration or at least the condensed electron configuration. So in this case, let's write the electron configuration 1S2, 2S2, 2P6, 3S1. So when we do that, we should realize this is the noble gas configuration there, noble gas neon. And it's got 6, 2, 2, so that's 10 electrons. And do you guys see any d orbitals up there, any f orbitals? So plus 0 electrons plus 0 electrons. So another name for these inner electrons you might see is core electrons, sometimes I'll say that. So the number of core or inner electrons in the sodium atom is 10 electrons. Is everybody OK with that? So how do I figure out the effective nuclear charge? So remember, capital Z is nuclear charge. So Z effective is going to be the total nuclear charge. Minus the number of inner electrons, or core electrons. Do you prefer? And so Z total for sodium, we have to again look at the periodic table. It's 11 minus the number of inner electrons. Now, this is just the number, OK? So don't try to make it a negative. And when we do that, it's good to put a positive there, honestly, because it's an overall positive effective nuclear charge. So the Z effective, or the sodium atom, is going to be plus 1. And the number of inner electrons. And see the oxidation of the like, plus 1. Do it this way, OK? It'll come in helpful when we're doing like transition metals and things like that. So just get used to doing it this way, OK? Any other questions?