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The sum of the numbers of protons and neutrons in an atom, an integer.

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  • Use of diamonds

    Diamond is a crystalline modification of pure carbon formed in the deep interior of the Earth, in the upper mantle at depths of more than 80-100 kilometers, at exceptionally high pressure and temperature. It is the most precious stone, the hardest and most wear-resistant mineral, the most...

  • Interesting facts about metals

    Metals have been used by people since ancient times. All the time the process of obtaining them was improved, useful alloys of various metals appeared. Let’s look at interesting facts about metals.

  • Varieties of garnet minerals

    The most famous type of garnet stone is pyrope (flaming). This is the "oldest of garnets", with a dense red color, similar to the grain of an edible garnet. Pyrope has a variety called rhodolite - a stone of dense pink or pink-purple color, which sometimes has the alexandrite effect and is used in...

  • Features of the Scanning Tunneling Microscope

    The scanning tunneling microscope (STM) invented by Heinrich Rohrer and Gerd Binnig in the 1980s still manages to do a great job today and competes with more advanced microscope types. The scanning tunneling microscope is used for studying the surface atoms that are found on various materials. The...

  • The most expensive metal in the world

    Do you think the most expensive metal is gold? No! On earth there are more valuable metals. But we need to divide the value of metals that occur in nature, and metals - isotopes, which are obtained in special laboratories. Let’s look at natural metals first.

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Absolute Zero

The zero point on the absolute temperature scale, -273.15°C or 0 K, theoretically, the temperature at which molecular motion ceases. The concept of an absolute zero temperature was first deduced from experiments with gases. When a fixed volume of gas is cooled, its pressure decreases with its temperature. Absolute zero physically possesses quantum mechanical zero-point energy.


To estimate the value of a result outside the range of a series of known values. Technique used in standard additions calibration procedure.

Strong Electrolyte

A substance that conducts electricity well in a dilute aqueous solution.



A commercial term used to describe ethanol that has been rendered unfit for human consumption because of the addition of harmful ingredients to make it sales tax-expempt.


Functional Group

A group of atoms that represents a potential reaction site in an organic compound.

Oxidation-reduction Reactions

Reactions in which oxidation and reduction occur, also called redox reactions.

Lewis Dot Formula (Electron Dot Formula)

Representation of the core of a molecule, ion or formula unit by showing atomic symbols and only outer shell electrons.

Electron Configuration

Specific distribution of electrons in atomic orbitals of atoms or ions.


One of the two mirror-image forms of an optically active molecule.

Central Atom

An atom in a molecule or polyatomic ion that is bonded to more than one other atom.