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Radical A radical is a group of atoms that appear in a compound and act as a group. Functional groups are classified as radicals. Two examples are NaCl and NaOH. In these examples, the chlorine ion and hydroxide functional group bond in similar ways with the sodium atom.

More Information: Compounds
Radioactivity Radioactivity occurs when the nucleus of an atom breaks up into two or more pieces. A neutron is often released during radioactive decay.

More Information: Radioactivity
Radium Symbol:"Ra" Atomic Number:"88" Atomic Mass: 226.03amu. Radium is a member of the alkaline metals group. It was discovered by the Curies in 1898 and is a radioactive, white metal that is often luminescent (glowing). You will find it in use for medicine, glowing paints, and the creation of radon gas.

More Information: Alkaline Metals
Radon Symbol:"Rn" Atomic Number:"86" Atomic Mass: (222)amu. It is one of the noble or inert gases. This element has not been found in nature and is a product of some nuclear reactions and the combustion of heavier elements. It is very dangerous and toxic to living organisms.

More Information: Noble Gases
Raoult's Law This chemistry law shows that the vapor pressure above a mixture of two liquids is directly related to the amounts of the solute and solvents in the solution.

More Information: Liquids
Rate of Diffusion This rate measurement is the speed at which molecules or atoms diffuse through a substance.

More Information: Gases
Reactive Element When an element is reactive, it is easily excited. It can combine with other elements very quickly and get involved in many chemical reactions.

More Information: Elements
Real Gas A real gas is one that you find in the real world. They have unique properties depending on the temperature and pressure. A perfect gas would be called an ideal gas.

More Information: Gases
Regional Metamorphism Metamorphic rocks that have been formed in areas where heat and pressure combined to create the rock. Mountain areas are locations of regional metamorphism.

More Information: Solids
Relative Density When the absolute density of a gas is compared to the density of air. The comparison of two values makes it relative. Air has a relative density of 1.0.

More Information: Phases of Matter
Reniform Habit A shape of a large crystal which has the arrangement of several small rounded balls stuck together. Think about some of those computer generated structures of molecules for this example.

More Information: Crystals
Rhenium Symbol:"Re" Atomic Number:"75" Atomic Mass: 186.21amu. This is one of the transition elements. Rhenium is never found free in nature, always bonded to other elements. This silvery-white metal is used in many alloys, flash photography, and even experiments with super-conductivity.

More Information: Transition Metals
Rhodium Symbol:"Rh" Atomic Number:"45" Atomic Mass: 102.91amu. Rhodium is one of the transition elements and in the platinum family. Rhodium is often used to harden platinum and found in spark plugs and highly reflective materials.

More Information: Transition Metals
Rock A rock is a group of minerals in a mixture. Volcanic rocks are excellent examples of rocks created by the super-heated mixing of many minerals.

More Information: Solids
Rubidium Symbol:"Rb" Atomic Number:"37" Atomic Mass: 85.47amu. One of the alkali metal group. This silvery-white, metallic element can be found in many alloys and amalgams.

More Information: Alkali Metals
Ruthenium Symbol:"Ru" Atomic Number:"44" Atomic Mass: 101.07amu. Ruthenium is one of the transition elements. One of the members of the platinum group, this white metal can be found in alloys and corrosion resistant metals.

More Information: Transition Metals
Rutherfordium Symbol:"Rf" Atomic Number:"104" Atomic Mass: (261)amu One of the postactinide elements. Scientists have created these in labs and may have found only a few atoms of the element. You will not find these in use anywhere.

More Information: Transition Metals


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Related Links
Chem4Kids: Matter
Chem4Kids: Atoms
Chem4Kids: Elements
Chem4Kids: Periodic Table
Chem4Kids: Reactions
Chem4Kids: Biochemistry

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