electrons

[masti_88]

the velocity of electron is maximum in which orbital, the one closest to the nucleus or the farthest? and why?

[Teddio]

From a Newtonian perspective, treating the electrons as charged point masses, the electrons nearest the nucleus will have the highest orbital speed because they will experience the highest electric field strength. The situation is analogous to planets orbiting the Sun. Mercury has the highest orbital speed because it is nearest the Sun and is subject to the highest gravitational field strength.

[Physics girl]

The maths is pretty much the same as for planets - in other words, the time period squared is proportional to the radius cubed. The force from the nucleus gets quartered if the electron is twice as far, and is 1/9 the strength if 3 times further away, etc. This is why the force is much stronger near the nucleus, and although the electron doesn't travel as far round, it still travels much faster. Think of it like a car - a smaller bend can still be travelled faster if the tyres become much more, erm, grippy than they were on the larger bend. Again, this is a Newtonian perspective..

[jake-the-peg]

By the way all these answers have "from Newtonian perpsective" tacked on because from a Newtonian perspective the electrons should radiate energy and crash into the nucleus.

We now know that electrons are not like little planets hurtling around the nucleus but it's a good starting point as things start to get very complicated very fast when you start to open this particular can of worms.