energy of an electron and energy terminology in general

[northwestmedic]

hi, hoping people can help. this is really basic, but seems potentially confusing. and glossed over in all but most detailed textbook

part 1:

the further away an electron from the nucleus, the more energy it has.......

BUT.... the equation for energy of an electron has "radii squared" in the denominator.... therefore, as partial derivative, energy should go down

FURTHER, at infinite distance, the energy of the election is zero.

i don't understand this.. doesn't make sense to me......... i understand it's only a partial derivative. so bigger atoms have more charge and therefore the electrons have more energy.

but the basic concept seems backwards to me.. or at least poor explained. and i know it's something that bothered me in the past.

part 2 (various questions):

is there negative and positive energy values? i.e. attractive vs. repulsive force? or it is just an absolute number?

does the electron have energy or potential energy? or is that the same thing?......... is a barrell of oil have energy or potential energy? same with a giant boulder hanging off a large cliff?

lastly, what is the nature of the electron's energy (potential) energy? it's movement. it's attraction to protons.

thx in advance ........ i might need a 1200 page chemistry textbook vs. the various study guides i have handy

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[mvsrocks]

I was a Chem/Biochem major and can answer some of your questions!

For part 1, which equation are you referring to for energy of electron? In general, you need to put in energy to move an electron "farther" from the nucleus (ionization energy).

The total energy of an electron is relative, and we arbitrarily assign "0 energy" to be when the electron has enough energy to escape the atom. The electron has negative energy because it consumes energy to have the electron escape and reach "0 energy."

For part 2, an object's total energy (or just "energy") is the sum of kinetic energy and potential energy. Potential energy is only one component of energy (includes gravitational potential, chemical potential, electrical potential), and an electron in an atom has both kinetic and potential energy. For both the barrel of oil and boulder example, assuming that both are macroscopically stationary, you can say that they have potential energy (whether chemical or gravitational) but no macroscopic kinetic energy. Technically, things with non-zero temperature have kinetic energy on a microscopic level (atoms vibrating). If something has any form of energy (whether potential, kinetic, or both), it is said to have energy.

For your last question, you can think of things this way: if it's not kinetic energy, it's probably a type of potential energy. (light/electromagnetic radiation is an exception).