Question

what are valence electrons

Answer 1

Valence electrons are those electrons which are farthest from the nucleus.
Hence they are not as tightly attached by nuclear force as the ones near the nucleus.
This makes it easier for valence electrons to participate in the formation of chemical bonds with other atoms.
The lesser the number of valence electrons in outermost most orbit, more reactive is the element; like Alkali metals, Na, K which only have 1 valence electrons and give it up easily to form a positive ion.

Answer 2

The word 'valence' means capacity, so the valence number (number of valence electrons) gives you a measure of how many electrons the atom can donate or accept.

Answer 3

Valence electron are those...electrons which are present in the last orbital

Answer 4

they are the farthest electrons becoz they are in the outermost energy level is it, why the valence of any any atom is always between 1 and 8...

why the outermost energy level always stops at 's', 'p' sublevels, but not 'd' or 'f' sublevels ?

Answer 5

@sara12345 that has to do with the geometry of the electron arrangement. Since electrons are all negative charge, they all mutually repel each other. 8 electrons in the outer 'shell' has the most stable configuration.

Answer 6

why not 18 when we fill d sublevel fully, \(3s^23p^63d^{10}\)

Answer 7

i see that after \(3p^6\), the electrons go into upper shell, \(4s\) directly. they dont occupy the empty sublevel \(3d\) . thats exactly my question why this happens.. why outer most sublevels are alwasy s or p

Answer 8

This might give some explanation, but my short answer is that electrons (like everything else in nature) seek the lowest potential energy. Because of a combination of effects (Quantum Electrodynamics and Relativity), the lower sublevels don't necessarily have the lowest energy.

Also, my explanation about mutual repelling forces and the balance with attractive forces with the nucleus also play a part.

Answer 9

something like that reasoning only i need... thank you :)

so if i get it correctly, the 'd' sublevel in n=3 has more energy than 's' sublevel in n=4
is it ?

and there are some reasons which you've listed.. for that behavior

Answer 10

the '4s' sublevel has less energy compared to '3d' sublevel, even though '4s' is farther from the nucleus. is this correct ?

Answer 11

Sorry, meant to post this link with my last comment.
http://en.wikipedia.org/wiki/Electron_configuration

Answer 12

i went through wiki before and also my notes, this question still persists to bother me :(

Answer 13

"the '4s' sublevel has less energy compared to '3d' sublevel, even though '4s' is farther from the nucleus. is this correct ?"

I think that might be the easiest way to put it, yes.

Answer 14

is there the easy/simple reasoning to make sense of that behavior