Atomic Structure

Nuetron

*Neutrons are uncharged particles found within atomic nuclei. Neutrons were discovered by James Chadwick in 1932. *Experiments done at the Stanford Linear Accelerator Center in the late 1960's and early 1970's showed that neutrons are made from other particles called quarks. Neutrons are made from one 'up' quark and two 'down' quarks. *A neutron is one of the fundamental particles that make up matter. This uncharged particle exists in the nucleus of a typical atom, along with its positively charged counterpart, the proton. Protons and neutrons each have about the same mass, and both can exist as free particles away from the nucleus. In the universe, neutrons are abundant, making up more than half of all visible matter.

Electron

Electrons - negatively (-) charged particles located in specific energy levels surrounding the nucleus Electrons have a mass of nearly zero. * a very small particle of matter that has a negative charge of electricity and that travels around the nucleus of an atom *Electrons are negatively charged particles that surround the atom's nucleus. Electrons were discovered by J. J. Thomson in 1897.

Protons

Protons - positively (+) charged particles Protons and neutrons each are given an amu of 1 *Protons are positively charged particles found within atomic nuclei. Protons were discovered by Ernest Rutherford in experiments conducted between the years 1911 and 1919. Experiments done at the Stanford Linear Accelerator Center in the late 1960's and early 1970's showed that protons are made from other particles called quarks. Protons are made from two 'up' quarks and one 'down' quark.

Nucleus

Small, dense, positively charged center of the atom which contains most of the atom's mass •The nucleus contains the following subatomic particles: *Protons - positively (+) charged particles *Neutrons - particles that have no charge (neutral), but contribute to the atom's mass *A central or essential part around which other parts are gathered or grouped; a core: the nucleus of a city.

Atomic Mass

The atomic mass is the mass of the protons plus the mass of the neutrons. Atomic mass is recorded in the SI units: atomic mass units (amu). the total mass of the protons, neutrons, and electrons in a single atom when it is at rest. This is not to be associated or mistaken for atomic weight. Atomic mass is measured by mass spectrometry. You can figure the molecular mass of an compound by adding the atomic mass of its atoms.

Valence Electron

The electrons in the outermost energy level are called valence electrons *An electron in an outer shell of an atom that can participate in forming chemical bonds with other atoms. *The valence electrons are the electrons in the last shell or energy level of an atom. They do show a repeating or periodic pattern. The valence electrons increase in number as you go across a period. Then when you start the new period, the number drops back down to one and starts increasing again. *

Atomic Number

The number of protons in the nucleus is the atomic number of that atom The atomic number represents the number of protons (+) and is equal to the number of electrons (-). The atomic number is equal to the number of protons in an atom's nucleus. The atomic number determines which element an atom is. For example, any atom that contains exactly 47 protons in its nucleus is an atom of silver. The number of protons in an element.

Electron Cloud

an area around the nucleus where electrons are likely to be found orbiting the nucleus in several energy levels •The electron cloud contains several energy levels * the system of electrons surrounding the nucleus of an atom *Electron cloud is the region of negative charge surrounding an atomic nucleus that is associated with an atomic orbital. It is used to describe the area around an atomic nucleus where an electron will probably be.

Atoms

often referred to as the building blocks of matter. *Each element on the periodic table is composed of one type of atom and cannot be broken down into a simpler substance. *composed of smaller subatomic particles such as the proton, neutron, and electron *contain a nucleus surrounded by an electron cloud that consists of one or more energy levels. * There are 90 naturally occurring kinds of atoms. Scientists in labs have been able to make about 25 more. *Atoms are composed of three type of particles: protons, neutrons, and electron. Protons and neutrons are responsible for most of the atomic mass e.g in a 150 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).

Energy Levels

•The electrons in the outermost energy level are called valence electrons *As you may remember from chemistry, an atom consists of electrons orbiting around a nucleus. However, the electrons cannot choose any orbit they wish. They are restricted to orbits with only certain energies. Electrons can jump from one energy level to another, but they can never have orbits with energies other than the allowed energy levels. *Bigger Orbit = Higher Energy *