quick question on the bond between the protons and electrons

[lboogy]

Hi everyone,

 

I've just got a quick question which I hope people don't mind me asking! Regarding atoms that have a stronger bond between the protons and the electrons the bigger the atomic number is - can anyone tell me why? I would have assumed that due to the fact that while there may be more atoms giving it a higher charge, an atom with a higher atomic number will also have more electrons to bond with and therefore it's increased charge due to it's high atomic umber will be used up on more electrons, than an atom with a smaller atomic number which while it does have a smaller charge, also has fewer electrons to bond with.

 

Can anyone help?

 

thanks in advance!

[pioneer]

As an example, K is larger and heavier than Na. The K is more reactive than Na, because the Na will hold its final electron a little tighter. One part of the explanation has to do with the larger size of K. This causes this last electron to be a little further from the nucleus. The EM force potential decreases with distance. The second part, is connected to the extra positive charge of the larger K, relative to Na, causes K's inner electrons to be pulled in closer. This closeness better shields the outer electrons, so K last electron isn't held as tightly.

[swansont]

That trend is true as you go across a row on the periodic table — you add a proton and electron; the electrons in general will try and space themselves as far apart as possible to minimize their energy, so there is minimal screening. Thus the extra electron "sees" all of the protons, and the atomic radius gets a little smaller. But when you move down, you get the screening that pioneer describes.