The Atom

The Atom - Basic explanation

STRUCTURE OF THE ATOM

If the protons and neutrons in this picture were each 10 cm across, then the quarks and electrons would be less than 0.1 mm in size and the entire atom would be about 10 km across!

Everything in the Universe, including you, is made up of atoms. They are so small that a million of them fit across the width of a hair. Yet atoms themselves are made up of even smaller particles.

Matter has mass and takes up space. Atoms are basic building blocks of matter, and cannot be chemically subdivided by ordinary means.
The word atom is derived from the Greek word atmos which means indivisible. The Greeks concluded that matter could be broken down into particles to small to be seen. These particles were called atoms
Atoms are composed of three types of particles: protons, neutrons, and electrons. Protons and neutrons are responsible for most of the atomic mass e.g in a 150 lb person 149 lbs, 15 oz are protons and neutrons while only 1 oz. is electrons. The mass of an electron is very small (9.108 X 10-28 grams).
Both the protons and neutrons reside in the nucleus. Protons have a postive (+) charge, neutrons have no charge --they are neutral. Electrons reside in orbitals around the nucleus. They have a negative charge (-).
It is the number of protons that determines the atomic number, e.g., H = 1. The number of protons in an element is constant (e.g., H=1, Ur=92) but neutron number may vary, so mass number (protons + neutrons) may vary.
The same element may contain varying numbers of neutrons; these forms of an element are called isotopes. The chemical properties of isotopes are the same, although the physical properties of some isotopes may be different. Some isotopes are radioactive-meaning they "radiate" energy as they decay to a more stable form, perhaps another element half-life: time required for half of the atoms of an element to decay into stable form. Another example is Oxygen, with atomic number of 8 can have 8, 9, or 10 neutrons.

*Atoms are made of negatively charged ELECTRONS* orbiting a nucleus**
The NUCLEUS is made up of Neutrons which carry no charge, and Protons which carry a positive charge.
*The NEUTRON* is neutral.**
*The PROTON* is positively charged.**
Protons and Neutrons contain three particles called QUARKS. *
*These Quarks are held together by other particles called GLUONS.*
* *Quark is a word from a line in Finnegan's Wake* by James Joyce - 'Three quarks for Muster Mark'**

All atoms are composed of three particles - Protons, Neutrons, and Electrons.

The centre of a atom is called the Nucleus.

The nucleus contains protons and neutrons.

Protons and neutrons have virtually the same mass. Their mass is almost the same as that of a hydrogen atom, so the proton and neutron are given a relative mass of ONE, like the hydrogen atom.

Protons are positively charged, but neutrons are neutral.

The Proton has two up quarks, and one down quark.

The Neutron has one up quark, and two down quarks.

The Gluons carry what is called the strong force, which holds the quarks together.

The nucleus takes up a minute part of the volume of the whole atom.

More than 99.9% of the atom is empty space occupied by moving electrons.

Electrons have a mass of about 2000 times less than that of protons and neutrons.

Electrons are negatively charged. The negative charge on one electron just balances the positive charge of one proton.

The electrons move about the nucleus very rapidly. They tend to remain in layers or Shells, at different distances from the nucleus. They are held in orbit around the nucleus by what is called the electromagnetic force.

Properties of Protons, Neutrons and Electrons
Particle	Position within the atom	Mass relative to hydrogen	Charge
Proton	Nucleus	1	+1
Neutron	Nucleus	1	0
Electron	Shells	1/2000	-1

"When they broke open molecules, they found they were only stuffed with atoms. But when they broke open atoms, they found them stuffed with explosions".


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