Question

Why do atoms release energy while gaining the 1st electron?

Answer 1

Hello?

Answer 2

Any answers?

Answer 3

which classs ?

Answer 4

if in 10th then , [me in 10th]
when we were studying electricity we studied that in 1 electron there is 6.25 * 10^18 C
that is why when a electron is gain that the atom becomes stable energy is release!

Answer 5

Although Eea varies greatly across the periodic table, some patterns emerge. Generally, nonmetals have more positive Eea than metals. Atoms whose anions are more stable than neutral atoms have a greater Eea. Chlorine most strongly attracts extra electrons; mercury most weakly attracts an extra electron. The electron affinities of the noble gases have not been conclusively measured, so they may or may not have slightly negative values.
Eea generally increases across a period (row) in the periodic table. This is caused by the filling of the valence shell of the atom; a group 7A atom releases more energy than a group 1A atom on gaining an electron because it obtains a filled valence shell and therefore is more stable.
A trend of decreasing Eea going down the groups in the periodic table would be expected. The additional electron will be entering an orbital farther away from the nucleus. Since this electron is farther from the nucleus it is less attracted to the nucleus and would release less energy when added. However, a clear counterexample to this trend can be found in group 2A, and this trend only applies to group 1A atoms. Electron affinity follows the trend of electronegativity. Fluorine (F) has a higher electron affinity than oxygen and so on.

Answer 6

Why wouldn't they? At the center of each atom is a big positive charge. Positive charge attracts negative charge, i.e. electrons, and if you allow the electron to come closer to the positive charge, energy will be released. Simple as that.

What may be puzzling you is that this still happens even when the total charge on the atom is already zero. That is, you may be wondering why a fluorine nucleus of charge +9 still attracts electrons even after it already has 9 electrons circling it. Why doesn't the repulsive force from those 9 electrons on another electron exactly cancel the attractive force from the nucleus?

The answer is that those 9 circling electrons would have to be *perfectly* positioned for that *exact* cancellation to occur. For example, if they were smeared out in a perfect spherical shell around the nucleus, that would work. But if instead 6 were floating on the back side of the nucleus (from the new electron) and only 3 were on the front side, then the repulsive and attractive electric forces won't *exactly* cancel. Since the electrons are in motion around the fluorine nucleus all the time, wandering here and there, this kind of "unbalanced" (unsymmetric) situation happens all the time, and the attractive and repulsive forces often don't exactly cancel.

Well, but then, you might wonder, why don't they cancel on average, so that even if there are sometimes net attractive forces on a new electron, there are net repulsive forces just as often -- and it averages out to zero.

The answer to this is more subtle, and it has to do with the fact that for a given system states of lower energy are more common than states of higher energy. In this case, if an electron happens to accidentally come near a fluorine atom, then the electrons already in the fluorine atom will tend to move away from the new electron (because they're repelled from it) and the nucleus will tend to move toward the new electron (because it's attracted). You end up with the nucleus kind of in the middle, the 9 electrons kind of off to the left (say), and the new electron off to the right. This situation has lower energy than where the 9 electrons are *closer* to the new electron, and hence the net force is repuslive. So it's more likely to happen. So on average, the situation where the net force is attractive happens more often than where the net force is repulsive.

There is a limit to this, of course. It is rare that atoms will bind *more* than one electron. Second and higher electron affinities are quite often zero or positive, meaning it takes energy to attach an electron (and it falls off easily).

I think part of the problem is that you are thinking of the atom as a single charged object, and thinking that when the nucleus is balanced by the same number of electrons as it has protons, it has a charge of zero -- and therefore exerts no electric forces at all.

This is oversimplified to the point of incorrect. You should keep in mind that in actual fact a neutral atom has a *balanced* amount of positive and negative charges, and that therefore the electric forces it exerts *tend* to be balanced, and cancel each other out. But they don't necessarily do so all the time, and there are many consequenecs of that. A negative electron affinity for many atoms is one of them. Another is the existence of dispersion (London) intermolecular forces, which are responsible for the existence of liquid and solid states for the noble gases.