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periodicity (image (periodic table consists of boxes :
element name , …
periodicity
periodic table consists of boxes :
element name , symbol ,atomic number , atomic mass
the box is arranged in order of increasing atomic number into a series of the column called families
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Except for Hydrogen ,all of element on the left side of the table are METALS .The group I element are know as the ALKALI METALS
Alkali Metals they are so reactive ,alkali metals usually exist as compounds with other element
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.Periodic trends, arising from the arrangement of the periodic table
provide chemists with an invaluable tool to quickly predict an element's properties
Major periodic trends include:
electronegativity, ionization energy , electron affinity, atomic radius, melting point, and metallic character
atomic radius : half the distances between nuclei of identical atoms that are chemically bonded together
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electronegativity：of an element indicates the relative ability of its atoms to attract electron in chemical bond
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When atoms gain or lose electrons, the atom becomes an ion. When an atom gains an electron, it becomes a negatively charged ion that we call an anion
Anions are larger in size than their parent atoms because they have one or more additional electrons, but without an additional proton in the nucleus to help moderate the size.
When an atom loses an electron, it becomes a positively charged ion called a cation.
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periodic Law:
that when the elements are arranged by increasing atomic number ,there is a periodic repetition of their chemical and physical properties
