valence electron periodic table transition metals

Once you reach the fourth period and the transition metals they follow an 18 electron rule of stability, but it's the same idea as before in that they are attempting to fill their valence electron shells in order to become stable. This octet rule holds for elements in the second and third periods (or rows) of the periodic table. This need to gain a filled valance electron shell by having 8 valence electrons is known as the octet rule and explains why certain elements are stable or unstable despite being electrically neutral. Neon has 8 valence electrons which is a filled second electron shell and is therefore stable and will be unreactive since it does not need to take electrons from other atoms. And again this can be explained by neon's valence electron configuration which is: 2s^(2)2p^(6). Now if we take a neutral atom of neon, Ne, which is just to the right of fluorine, neon is practically the opposite of fluorine in terms of reactivity despite both being neutral atoms. In other words, it will react in such a way to gain a new electron and fulfill its valence shell. And since it's so close to being filled, it will desperately want an extra electron which it will take from any nearby atom to do so. But fluorine has 7 valence electrons, 1 away from being filled. The second electron shell holds a maximum of 8 electrons and 8 electron would be considered a filled valence shell and would therefore be stable and unreactive. And this is explained if we look at fluorine's valence shell (the second shell) electron configuration: 2s^(2)2p^(5). For instance, if we take an atom of fluorine, F, in it's neutral state it has no net charge however it is VERY reactive. So even if an atom is neutral, that is not necessarily its most stable state. And vise versa, something which is unstable is reactive and will engage in chemical reactions to reach a new state.

Stability meaning that something is unreactive, that it won't engage in some kind of chemical reaction to reach a new state. The valence shell meaning the outermost electron shell. So being stable when talking about valence electrons means that the valence shell has been filled completely (or half filled).

Valence electron periodic table transition metals