Answer:
The answer will be ：
In year 1869
Russian scientist named Dmitri Mendeleev
Chart called Mendeeleves periodic table
increasing atomic masses
physical and chemical properties.
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The answer is more protons than electrons.
Reactivity is an impetus For which a chemical substance undergoes A chemical either by itself or with another materialWith an overall release of energy
Covalent bond a chemical bond formed by two electrons that are shared between two atoms
ionic bond<span> a chemical bond formed by the electrostatic attraction between ions</span>
metallic bond<span> a bond characteristic of metals in which mobile valence electrons are shared among positive nuclei in the metallic crystal</span>
