Understanding Systems?! Atoms and Elements?!?

Question

Why do atoms of Group 1 elements lose electrons to form cations, while atoms of Group 17 elements gain electrons to form anions?!

Answer 1

In simple terms, all atoms try to react to have the same number of valence electrons as the closest noble gas. This gives them some stability. Group 1 elements are closer to the noble gas that comes just before them numerically. Na is closest to Ne, K is closest to Ar, etc. In order to have the same number of valence electrons as their closest noble gas they group 1 elements must give away one of their valence electrons. By giving away one electron these elements now have one more proton than electron so they form a 1+ ion.

The same reasoning goes for the group 7 elements. The noble gases closest to them have one more electron in the valence level. Elements in group 7 must gain one more electron to have the same number of valence electrons as the nearest noble gas. By getting one more electron than they have protons, these elements will form ions with a 1- charge.

Answer 2

A molecule is stable when all atoms have the outer shell either empty or full

The outer shell or valence shell has 8 electrons (exception the first which has only 2 electrons.

In group 1 the atoms have single electron on the outer shell. This electron is easy to withdraw to have an empty shell

In opposite the atoms of group 7 (and not 17!!!) have 7 electrons .

It is easy for them to take an electron to fill this outer shell

Answer 3

It's a matter of ionization potential.
It's also a matter of electrostatics. To get a full electron shell, potassium can either lose one electron, or gain 7. Those 7 electrons would repel each other so much the atom would be enormous - the extra electrons would literally fly away as the positive charge in the nucleus would not be sufficient to hang on to them.

Answer 4

when u've asked the quest it's supposed that u know a lower potential energy corresponds to stabler state. elements of IA lose e- that is loosely held to release a lot of energy while VIIA elements do so by taking an e- and but both reach noble gas configuration. for instance if you put Na(s) in water it reacts vigourously and reactivity increases down due to increasing atomic size. Li reacts a bit less actively with water because of higher charge density n' hence unstebility of Li+ as stabitlity of ions is seen in gaseous state. if u don't understand anything send me back. i'm abhineet, 17 ,preparing for iit.