Name: 週期變化趨勢和庫侖定律｜原子結構和性質｜AP化學｜可汗學院 (Periodic trends and Coulomb's law | Atomic structure and properties | AP Chemistry | Khan Academy)
Uploaded: 2021-01-14T10:13:41.000Z
Duration: 10 min 43 s
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- [Instructor] In this video we're going to look at trends

atomic and ionic radii, electron affinity,

a very fundamental idea in chemistry or physics,

And for our point of view, we can view Coulomb's Law

as saying that the magnitude of the force

between two charged particles is going to be

proportional, that just means proportional right there,

is going to be proportional to the charge

on the second particle, divided by the distance

of the periodic table of elements and various atoms,

you can view q1 as the effective positive charge

from the protons in the nucleus of an atom.

You can view q2 as the charge of an electron.

the same negative charge, but as we try to understand

it's really the outer most shell electrons,

the valence electrons, that are most interesting.

Those are the ones that describe the reactivity.

between the two charges we're mainly going to be

thinking about the distance between the nucleus

I'll call it z-effective, as being equal to the difference

so you can just view this as the atomic number,

that a given element or an atom of that element has,

and the difference between that and what is often known as

Now there is complicated models for that,

this is often approximated by the number of core electrons.

what's going on with the valence electrons.

do that orange color, that has protons in it.

Let's say these are the core electrons in the first shell,

and then you have some core electrons in the second shell.

And let's say the valence electrons are in the third shell.

So let's say these are some valence electrons here,

they're blurred around, they're in these orbitals.

Those valence electrons, which have a negative charge,

are going to be attracted to the positive charge

of the nucleus but they're also going to be

of the effective charge that these valence electrons

might experience is going to be the charge

of the nucleus minus, and this is an approximation,

the number of core electrons that you have.

So if we use that roughly as a way to think about

z-effective, what do you think are going to be

the trends in the periodic table of elements?

Lithium atomic number of 3, minus 2 core electrons

that are in 1-S, so once again you're going to have

So roughly speaking, all of these Group I

Well if you look at Flourine, atomic number of 9,

Chlorine actually has an effective charge of 7

Atomic number of 17, but 10 core electrons.

is going to have an effective charge of 2,

atomic number of 2 minus 0 core electrons.

And you'll see as you go down these noble gases,

other than Helium, they have an effective charge of 8.

And so the general trend is, your effective charge is low

at the left, effective charge low for Group I,

and then when you go to the right of the periodic table,

you have a z-effective, is going to be high.

So within a given period, or within a given row

your outer electrons, your valence electrons,

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週期變化趨勢和庫侖定律｜原子結構和性質｜AP化學｜可汗學院 (Periodic trends and Coulomb's law | Atomic structure and properties | AP Chemistry | Khan Academy)

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