Quark

Quarks and electrons are the tiniest particles. There are three quarks in every proton and three in every neutron, and protons and neutrons are the pieces of an atom. We can't see a quark, even with an electron microscope, but we know they must exist because that's the only way to explain what happens when scientists do certain experiments.

The first quarks probably came into being just at the time of the Big Bang, right at the beginning of the universe. At that time, there was nothing in space but lots of electrons and quarks, and positrons and anti-quarks. But quarks don't like to be alone, so less than a second after the Big Bang the quarks were already teaming up to make protons and neutrons. After less than five minutes, the protons and neutrons were already joining up with the electrons to make hydrogen and helium atoms.

There are six kinds of quarks - up quarks, down quarks, strange quarks, charm quarks, bottom quarks, and top quarks. Their names don't really mean anything, just that they are different kinds of quarks. A proton is made of two up quarks and a down quark, and a neutron is made of two down quarks and an up quark. A force called the strong nuclear force holds the quarks together. Up quarks have a little bit of mass, but most of the mass of a proton comes from the strong nuclear force itself, rather than from the quarks.

What is an Atom

Atoms are the basic building blocks of ordinary matter. Atoms can join together to form molecules, which in turn form most of the objects around you.

Atoms are composed of particles called protons, electrons and neutrons. Protons carry a positive electrical charge, electrons carry a negative electrical charge and neutrons carry no electrical charge at all. The protons and neutrons cluster together in the central part of the atom, called the nucleus, and the electrons 'orbit' the nucleus. A particular atom will have the same number of protons and electrons and most atoms have at least as many neutrons as protons.

Protons and neutrons are both composed of other particles called quarks and gluons. Protons contain two 'up' quarks and one 'down' quark while neutrons contain one 'up' quark and two 'down' quarks. The gluons are responsible for binding the quarks to one another.

Atomic Number and Mass

Atomic Number

The number of protons in the nucleus of an atom determines an element's atomic number. In other words, each element has a unique number that identifies how many protons are in one atom of that element. For example, all hydrogen atoms, and only hydrogen atoms, contain one proton and have an atomic number of 1. All carbon atoms, and only carbon atoms, contain six protons and have an atomic number of 6. Oxygen atoms contain 8 protons and have an atomic number of 8. The atomic number of an element never changes, meaning that the number of protons in the nucleus of every atom in an element is always the same.

Atomic Mass

The Number of Protons and Neutron is known as Atomic Mass

            Protons + Neutron = Atomic Mass

What is a Molecule

Molecule

A molecule is the smallest particle in a chemical element or compound that has the chemical properties of that element or compound. Molecules are made up of atom s that are held together by chemical bonds. These bonds form as a result of the sharing or exchange of electron s among atoms.
The atoms of certain elements readily bond with other atoms to form molecules. Examples of such elements are oxygen and chlorine. The atoms of some elements do not easily bond with other atoms. Examples are neon and argon.
Molecules can vary greatly in size and complexity. The element helium is a one-atom molecule. Some molecules consist of two atoms of the same element. For example, O ₂ is the oxygen molecule most commonly found in the earth's atmosphere; it has two atoms of oxygen. However, under certain circumstances, oxygen atoms bond into triplets (O ₃ ), forming a molecule known as ozone. Other familiar molecules include water, consisting of two hydrogen atoms and one oxygen atom (H ₂ O), carbon dioxide, consisting of one carbon atom bonded to two oxygen atoms (CO ₂ ), and sulfuric acid, consisting of two hydrogen atoms, one sulfur atom, and four oxygen atoms (H ₂ SO ₄ ).
Some molecules, notably certain proteins, contain hundreds or even thousands of atoms that join together in chains that can attain considerable lengths. Liquids containing such molecules sometimes behave strangely. For example, a liquid may continue to flow out of a flask from which some of it has been poured, even after the flask is returned to an upright position.
Molecules are always in motion. In solids and liquids, they are packed tightly together. In a solid , the motion of the molecules can be likened to rapid vibration. In a liquid, the molecules can move freely among each other, in a sort of slithering fashion. In a gas , the density of molecules is generally less than in a liquid or solid of the same chemical compound, and they move even more freely than in a liquid. For a specific compound in a given state (solid, liquid, or gas), the speed of molecular motion increases as the absolute temperature increases.

What are Isotopes

Isotopes

Atoms of the same element can have different numbers of neutrons; the different possible versions of each element are called isotopes. For example, the most common isotope of hydrogen has no neutrons at all; there's also a hydrogen isotope called deuterium, with one neutron, and another, tritium, with two neutrons.

Hydrogen		Deuterium		Tritium

If you want to refer to a certain isotope, you write it like this: ^AX_Z. Here X is the chemical symbol for the element, Z is the atomic number, and A is the number of neutrons and protons combined, called the mass number. For instance, ordinary hydrogen is written ¹H₁, deuterium is ²H₁, and tritium is ³H₁.

What is Radio Activity

Atoms are found in all natural matter. There are stable atoms, which remain the same forever, and unstable atoms, which break down or 'decay' into new atoms. These unstable atoms are said to be 'radioactive', because they emit radioactivity from the nucleus as they decay.
Radioactive elements, such as uranium, thorium and potassium break down (decay) fairly readily to form lighter atoms. The energy that is released in the process is made up of small, fast-moving particles and high-energy waves. These particles and waves are, of course, invisible. (The level of radioactivity of an element varies according to how stable its atoms are). Other elements with naturally occurring radioactive forms, (isotopes) are carbon, bismuth, radon, and strontium.
Radioactivity is a random process that happens naturally as the isotopes in particular elements decay. The isotopes continue to break down over time. The length of time that is taken for half of the nuclei in an element to decay is called its 'half-life'. A half-life can be very short (milliseconds to hours) or very long (hundreds of thousands of years).
Radiation also arises from nuclear fission. Fission can be spontaneous but is usually initiated in a nuclear reactor. Fission is a radioactive process; it releases energy as the heavy nucleus is split into two.

What is An Element

An element is a substance that is made entirely from one type of atom. For example, the element hydrogen is made from atoms containing a single proton and a single electron. If you change the number of protons an atom has, you change the type of element it is.

If you had very, very good eyes and could look at the atoms in a sample of hydrogen, you would notice that most of the hydrogen atoms would have no neutrons, some of them would have one neutron and a few of them would have two neutrons. These different versions of hydrogen are called isotopes. All isotopes of a particular element have the same number of protons, but have a different number of neutrons. If you change the number of neutrons an atom has, you make an isotope of that element.

As of October 16, 2006, scientists know of 117 different elements. Some, like gold, silver, copper and carbon, have been known for thousands of years. Others, such as meitnerium, darmstadtium and ununquadium, have only recently been created by scientists. All known elements are arranged on a chart called the Periodic Table of Elements.

What is Molecular Farmula

The molecular formula specifies the actual number of atoms of each element in a molecule.
The conventional form for writing a molecular formula is to write the symbol for each element followed by a subscript indicating the actual number of those atoms present in a molecule. When only one atom of an element is present, the subscript is omitted. For example, the molecular formula for water, H₂O, specifies that there are two hydrogen atoms and one oxygen atom present in each molecule of water.
It is important to remember that the molecular formula—in contrast to the simpler empirical formula that specifies only the relative number of atoms or moles present in a compound—identifies the actual number of atoms present in a molecule.

What is Molar Mass

Molar mass is closely related to the relative molar mass (M
r) of a compound, the older term formula weight and to the standard atomic masses of its constituent elements. However, it should be distinguished from the molecular mass (also known as molecular weight), which is the mass of one molecule (of any single isotopic composition) and is not directly related to the atomic mass, the mass of one atom (of any single isotope). The dalton, symbol Da, is also sometimes used as a unit of molar mass, especially in biochemistry, with the definition 1 Da = 1 g/mol, despite the fact that it is strictly a unit of molecular mass (1 Da = 1.660 538 782(83)×10⁻²⁷ kg).
Molar masses are almost never measured directly. They may be calculated from standard atomic masses, and are often listed in chemical catalogues and on material safety data sheets (MSDS). Molar masses typically vary between:

1–238 g/mol for atoms of naturally-occurring elements;

10–1000 g/mol for simple chemical compounds;

1000–5,000,000 g/mol for polymers, proteins, DNA fragments, etc.

Periodic Table