# Why does increasing orbital energy mean an electron can be more easily lost?

Why is the higher the orbital energy, the easier the electron lost? Also, if the distance between the electron and nucleus is getting father，the electronegativity is getting weaker, the electron is getting easier to lost? I feel confused about this two concepts.

Why is the higher the orbital energy, the easier the electron lost?

Orbital energies are measured relative to an electron at infinity (i.e. one which has been ionized), which corresponds to an energy of 0 eV. An electron which is lower in energy than this (i.e. bound to an atom) has a negative energy. The first six energy levels for hydrogen are shown above. As you can see, the energies converge to 0 as n, the principal quantum number, goes to infinity. In order to ionize an electron it must be given enough energy to promote it to the n = ∞ energy level. Therefore the higher the energy of the electron, the less energy is required to ionize it.

Also, if the distance between the electron and nucleus is getting father，the electronegativity is getting weaker, the electron is getting easier to lost?

The most likely distance of the electron from the nucleus (the maximum in the orbital's radial distribution function) increases with n and so the electron is in a higher energy orbital and is more easily lost.

1) As we go farther from the nucleus, the energy of orbitals increase. Also, the farther an electron is from the nucleus, the more repulsions it has to face because of other electrons(more screening effect) and hence it is easier to remove that electron.

2) As the distance between the nucleus and the electron increases, electronegativity gets weaker. It's true but we use this while comparing electronegativity of various elements and not for a particular element. For any particular element , its electronegativity is always fixed, because it's just the tendency of that atom to attract electrons and nothing else.

• For any particular element , its electronegativity is always fixed, because it's just the tendency of that atom to attract electrons and nothing else. No it isn't. It depends on the oxidation state of the atom - or in organic chemistry this is usually viewed in terms of hybridisation rather than oxidation state.
– bon
Mar 8, 2016 at 19:14

See its related to screening effect which is denoted by $Z^*$ and $Z^*=Z-a$ where z is nuclear charge and a is atomic number as distance increases the effective charge of nucleus decreases resulting in loss of electron to attain stability .Higher energy implying farther orbitals . and as distance increases electronegativity decreases down the group like $H>Na$ thus na us more reactive than H where H,Na are hydrogen,sodium