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Q & A: What do electrons want?

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Most recent answer: 02/10/2013
Q:
Why do people talk about electrons and atoms "wanting" to do certain things? This can't be an accurate way of saying it. Electrons don't have personalities. Surely they don't like /dislike anything. Examples "The atom WANTS to have a full outer shell", "the electron WANTS to leave sodium's outer shell because it isn't HAPPY there and fill up chlorine's outer shell". What is a more scientific way of saying this without going into too much detail?
- Amy (age 12)
Broadstairs, UK
A:
Amy- You make a good point. We've touched on the same issue before: .

What do we usually mean when we say that a physical system "wants" to be some way?  Often it's that the physical system can lower its energy that way. You tend to find the system going from the high energy initial state to the lower energy one as if it "wanted" to be in the low energy one.

The reason things act that way is that there's a very general principle that nature drifts on its own into just any old state. Thus in the long run what you see is almost certain to be what most states look like. But wait- why would that mean we'd be more likely to see the lowest energy state of our little object? That's because as it dumps its extra energy to the rest of the world, the rest of the world gets more states.

If we look at a somewhat larger object, it "wants" to have low "free energy", not low energy. Free energy is a quantity that partly depends on how many states the object itself could be in, and partly on how much energy it gives away to the surroundings,  letting them reach more states. We say that reaching low free energy maximizes the total entropy, which is a number used to keep track of the number of possible states.

So the ultimate explanation of the why nature seems to "want" certain conditions is that nature is totally indifferent to what quantum states it ends up in. Thus if you want to predict how things will end up, you bet on the biggest number of possible states. The appearance of intent is produced by the complete absence of intent.

Mike W.

(published on 02/10/2013)

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