Mendeleev arranged the elements according to their atomic masses
Elements in the same group have D. Same number of valence electrons.
Nonpolar covalent bonds are chemical bonds where two atoms share a pair of electrons with each other and the electronegativities of the two atoms are equal. An example is methane. It has four carbon-hydrogen single covalent bonds. These bonds are nonpolar because the electrons are shared equally.
Carbon monoxide (CO) is the name
I believe the major periodic trends include; electronegativity, ionization energy, electron affinity, atomic radius, melting point, and the metallic character. Periodic trends, arising from the arrangement of the periodic table, provide chemists with an invaluable tool to quickly predict an element's property.