The Periodic Table of the Elements
Synonyms: Periodic chart
The Periodic Table of the Elements is a systematic arrangement of the elements according to their atomic number and chemical properties. The atomic number indicates the number of protons in the nuclei. Atoms in the same group share a number of chemical similarities, e.g. the atoms in group one - the alkali metals - all has a single electron in the outer shell. These atoms reacts easily with atoms from the 17'th group - the halogens - and creates salts like NaCl (sodium chloride) and KBr (potassium bromide). In the 18'th group the noble gasses are found, these gases are nonreactive to such a degree that they seldom reacts with other atoms. As a consequence they exists as monoatomic gases.
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