Definitions

Atomic
Number
(Protons)
Symbol
(Radioactive)
Atomic
Weight
(Average)
Element Name (Group color)

Group/Classifications

    Alkali Metals
    Alkaline Earth Metals
    Transition Metals
    Other Metals
    Metalloids
    Nonmetals
    Halogens
    Noble Gases

Atomic Number

Number of protons / electrons in an atom of  neutral charge.

Atomic Weight

Weighted average of atomic masses of natural isotopes, or mass number of the most stable isotope for each radioactive element.

Electron Configuration

Click Here!

Oxidation States

Most important state in bold

Electronegativity

Pauling scale; measures ability of atom to attract electrons in a chemical bond.

Atomic/Ionic Radii

pm Pico-Meter = 1x10-12m

Electron Affinity

Energy released in the formation of an anion; given in "eV".

1st Ionization Potential

Energy required to remove one electron, forming a cation; given in "eV".

Natural Form

State of element at 25C and 1 atmosphere pressure

Stable Solid Crystal

Cubic Simple Cubic
BCC Body Centered Cubic
FCC Face Centered Cubic
Hex Hexagonal
Ortho Orthorhombic
Rhom Rhombohedral
Tetra Tetragonal
Mono Monoclinic
    - Unknown

Density

Solids g/cm3, 20C and 1Atm
Liquids g/cm3, 20C and 1Atm
Gases g/liter, 0C and 1Atm

Enthalpy of Vaporization

Liquid > Gas
dHvaporization at b<0.001 Point
(kJoule/mole)

Enthalpy of Fusion

Solid > Liquid
dHfusion at Melting Point
(kJoule/mole)

Boiling Temperature

Liquid <> Gas, C and 1Atm
sp = Boiling Sublimation Point

Melting Temperature

Solid <> Liquid, C and 1Atm
tp = Melting Triple Point

Electrical Conductivity

ResistanceOhms =
Length/(n x 106 x Area)

Where Temperature is 25C, Length is in cm and Area is cm2.  A 1 cm3 block of copper would be 1.677 x  10-6 ohms at 25C.

Isotopes

Major natural isotopes with % of occurrence:  Isotopes have the same number of protons but different numbers of neutrons.  Isotopes not listed are radioactive or synthetic.  Radioactive isotopes highlighted in red.

Alpha Decay

An ALPHA PARTICLE is an ionizing radiation that consists of two protons and two neutrons. The neutrons and protons give the alpha particle a relatively large mass as compared to other ionizing radiation particles. Because of this large size, the alpha particle has a relatively low speed and low penetrating distance (one or two inches in air). The particle tends to travel in a straight line, causing a large number of ionizations in a small area.  Alpha particles are easily shielded (or stopped) by a thin sheet of paper or the bodys outer layer of skin. Since they do not penetrate the outer (dead) layer of skin, they present little or no hazard when they are external to the body. However, alpha particles are considered to be an internal hazard, because they can be in contact with live tissue and have the ability to cause a large number of ionizations in a small area. INTERNAL and EXTERNAL HAZARDS refer to whether the radioactive material is inside the body (internal) or outside the body (external).

Beta Decay

A BETA PARTICLE is a high speed ionizing radiation particle that is usually negatively charged. The charge of a beta particle is equal to that of an electron (positive or negative), and its mass is equal to about 1/1800th of that of a proton or neutron. Due to this relatively low mass and charge, the beta particle can travel through about 10 feet of air and can penetrate very thin layers of materials (for example, aluminum). However, clothing will stop most beta particles. The beta particle can penetrate into the live layers of the skin tissue and is considered both an internal and an external hazard. Beta particles can also be an external hazard to the lens of the eye. Beta particles are best shielded by thin layers of light metals (such as aluminum or copper) and plastics.

Gamma Decay

A GAMMA RAY is an ionizing radiation in the form of electromagnetic energy (no rest mass, no charge) similar in many respects to visible light (but far more energetic). Due to the high energy, no charge, and no rest mass, gamma rays can travel thousands of feet in air and can easily pass through the human body. Because of their penetrating capability, gamma rays are considered both an internal and external hazard. The best shielding materials for gamma rays are very dense materials such as lead, concrete, and uranium.

Neutron Decay

The NEUTRON PARTICLE is an ionizing radiation emitted by nuclear fission and by the decay of some radioactive atoms. Neutrons can range from high speed, high energy particles to low speed, low energy particles (called thermal neutrons). Neutrons can travel hundreds of feet in air and can easily penetrate the human body. Neutrons are considered both an internal and external hazard, although the likelihood of an internal, neutron emitting, radioactive material is extremely unlikely. The best shielding materials for neutrons would be those that contain hydrogen atoms, such as water, polyethylene, and concrete. The nucleus of a hydrogen atom contains a proton. Since a proton and a neutron have almost identical masses, a neutron hitting a hydrogen atom gives up a great amount of its energy, and therefore, the distance traveled by the neutron is limited. This is like a cue ball hitting another billiard ball. Since they are the same size, the cue ball can be made to stop and the other ball will start moving. But, if a ping pong ball is thrown against a bowling ball, the ping pong ball will bounce off with very little change in velocity, only a change in direction. Therefore, heavy atoms, like lead, are not good at stopping neutrons.