# Atomic particles: size?

#### gendou

does anyone know if the atomic particles (protons, neutrons, electrons) have a particular size/shape? perhaps the idea of them having a certain radius is an imaginary concept? i would love to hear a knowledgeable opinion!

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#### garys_2k

No "particular" size or shape, at that level you have clouds of probability, depending on how they're packed, their energy levels, that sort of thing. One thing they are NOT are tiny little balls, as usually illustrated.

#### FZ+

Actually, I just wonder... What is the significance of size relating to a fundamental particle? I mean, when we talk of a billiard ball or whatever, our measure of size comes from the structure of EM force interactions it maintains, holding the individual bits apart a certain distance where they are in equilibrium and so on. But when we talk of individual leptons... how can we measure them?

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#### gendou

thanks FZ+ and garys_2k! i was wondering the same thing, i would agree that the classic model of "shape" doesnt work in a subatomic context.

#### PRodQuanta

What Garys_2k was saying about "clouds of probability" is also known as Heisenburg's Uncertainty Principle. This states that it is impossible to measure the momementum and the position of a particle simultaneously. This implies that an object is always in motion. So we can't measure a particle at a standstill, which makes it impossible to determine it's size or shape, but we can measure one more accurate and another not so accurate. This is what garys_2k means by clouds of probability.

I think that a particle's shape is determined by a 1-dimensional string that is vibrating at different frequencies with different tensions to the string. A.k.a String theory. But I won't get into that.

#### Gale

they have mass though right? do they not have volume? or just not definate shape? and hows about desnity?

#### elas

As an amateur theorist I take an interest in the size of atoms and particles. The size of both have been detected using various types of experiments, there is even an experiment for measuring the nucleus of atoms based on the average of thousands of X-rays.
Earlier experiments based on blocks of material produced atomic radii in physics and molar radii in chemistry. I used both to determine the volume and compared the results; there is a general agreement in about 90% of the elements.
I have also found a theoretical agreement between mass and volume of fundamental particles using arbitrary numbers.
The problem in grasping the reality of particles comes from our inability to visualise fields and our determination to see particles and atoms in terms of mass and/or energy. It is the field force(not the size or mass) that is always conserved.

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