<p>
[QUOTE]
Each shell holds a certain number of electrons. The innermost shell, designated as K, has 2; the next shell, L, can hold 8;** the third shell, M, also 8**; etc. When an atom has a shell that does not have a complete set of electrons, it is said to be structurally unbalanced, and will tend to interact with other atoms. The chemical activity of an atom, then, arises from the number of electrons in its outer shell
[/QUOTE]
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<p>I wonder why the third shell can hold 8 electrons. I thought M is the 3s 3p 3d, which can hold up to 18: 3s--2 3p--6 3d--10</p>
<p>2+6+10=18 ???</p>
<p>What do you think?</p>
<p>Isn't the order of electron level...shells "3s2, 3p6, 4s2, 3d10"?
If you look at the periodic table, 4s2, 3d10 (the transition metals) are in the next period down.</p>
<p>But I only mention the third shell.
This shell can hold 18 electrons at most. But the book says it can hold 8???</p>
<p>Yeah...the third shell is 3s2 3p6 --> 2 + 6 = 8
Period 1 has a max of 2 valence electrons --> 1s2
Period 2 has a max of 8 --> 2s2, 2p6
Period 3 has a max of 8 --> 3s2 3p6
Period 4 has a max of 16 --> 4s2 3d10 4p6
etc.</p>
<p>The book is wrong, at the very least in its terminology. CDN_Dancer, you're looking at the order in which shells are filled in a neutral atom, but you're splitting up actual shells; "4s2, 3d10, 4p6" is NOT a shell. A shell is 4s2, 4p6, 4d10, 4f14, for example.</p>
<p>So shell 1, or n=1, can hold 2 (1s2).
Shell 2, or n=2, can hold 8 (2s2, 2p6).
Shell 3, or n=3, can hold 18 (3s2, 3p6, 3d10), even though the subshells are not filled in this order in a neutral atom.
Shell 4, or n=4, can hold 32 (4s2, 4p6, 4d10, 4f14)
...and so on.</p>
<p>Thanks, everyone.
I agree with GoldShadow!</p>