What are atoms?

Answer 1

When you divide a block of a homogenous body (say some quantity of clean water, or a piece of chalk, or an ice cube, but not some quantity of soup or hazelnut chocolate) into smaller pieces by mechanical means, all the pieces that you get have the same chemical properites as the original body (the water is the same in every cup, but the hazelnuts are not the same as the chocolate). So, scentists and philosophers have been asking themselves whether this division process can go one forever or stop at some stage.

Well, todays science has proven (!) that there are some most simple pieces of the substances that carry all there chemical properites - these are called atoms for the most simple substances, called chemical elements, and moleculs for the more complex ones, called chemical compounds.

The atoms are really small and that makes it hard to to see them. Actually, they are smaller than the wavelength of the visible light, so you can't see them with an optical microscope. But, you can with a Scaning Electron Microscope, where the wavelength of the electrons is of the same order of magnitude as the atomic dimensions. But, even before people constructed electron microscopes, they have been able to indirectly prove the real existence of atoms (Brownian motion and diffusion, for example).

The word 'atom' comes from the Ancient Greek's word 'atomos' which means indivisible. Acctualy, atoms are only indivisible by chemical processes. When you ionise a gas, you separate one or more electrons from its outer shell and the remining positive ion no longer has all the chemical properities of the neutral atom. Also, scientists have even managed to separate the constituting elements of the nucleus: protons and neutrons. Actually, the nuclear reactors work on the ability to split the atomic nuclei into smaller fragments, but that's another story.

According to the Standard Model, protons and neutrons are baryons from the first generation of u (up) and d (down) quarks. Each of the baryons is consisted of 3 quarks, so you can make:

C'(2, 3) = C(4, 3) = 4

baryons with these 2 quarks:

uuu, uud, udd and ddd

Of these, uud coresponds to a proton (p), and udd to a neutron (n). The other 2 are more exotic ones, with charges +2e and -2e and I can't remember their name. Added to the 2 quarks, there is a pair of leptons: the electron (e) and the electron neutrino (nu - e). With these you can construct all the 'ordinary' matter. It is a curious fact that the reaction:

p + e -> n + nu-e

is endoenergetic and cannot happen for free protons and electrons, so the hydrogen atom is a stable structure. What holds the electrons in an atom is the electrostatic Coloumb attractive force.

Answer 2

Atoms are component mass structures forming and composing the materials of the Earth,Stars and Galaxies.
The orginal word come from the Greek language meaning "cannot be divided".Perhaps the Greek scientist Democritus,may have meant the particles of the space in the Universe. We know today that atoms can be divided and split.
So the assumption that he meant the substance of space is a more plausible premise.

Answer 3

An atom consists of a nucleus, protons and electrons. The protons are positively charged and the electrons are negatively charged. They atract each other making elements.

Answer 4

unit of matter, the smallest unit of an element, having all the characteristics of that element and consisting of a dense, central, positively charged nucleus surrounded by a system of electrons. The entire structure has an approximate diameter of 10-8 centimeter and characteristically remains undivided in chemical reactions except for limited removal, transfer, or exchange of certain electrons

Answer 5

Atoms, are the smallest units that chemical reactions occur.

Answer 6

Extremely small particles that are the basic building blocks of the universe. They make up absolutely everything from the air you breathe to the chair you sit on.

Answer 7

Small particles that everything is made up of, containing protons, neutrons and electons

Answer 8

Small particles that everything is made up of, containing protons, neutrons and electons

Answer 9

the tiny parts that make up everything on the planet they are a ten billionth of a millimetre

Answer 10

They are what everthing is made from. Yes everything