A group is any column on the periodic table. Elements in the same group usually have similar properties, because they have the same number of electrons in the outermost electron shell. There are eight main groups of elements, numbered 1, 2, and 13-18. The other ten groups are transition metals:
See Alkali metal
The most reactive metals are Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr)
See Alkaline earth metal. They are Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), Radium (Ra)
See Transition metals. Transition Metals are the most number of elements in the periodic table. They are Iron (Fe), Copper (Cu), Zinc (Zn), Chromium (Cr), Cobalt (Co), Nickel (Ni), Manganese (Mn), Mercury (Hg), Scandium (Sc), Titanium (Ti), Vanadium (V), Silver (Ag), Gold (Au), Cadmium (Cd), Tungsten (W), Platinum (Pt), Yttrium (Y), Molybdenum (Mo) and others.
The noble gases are the 18th group in the periodic table. They are Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn). They were previously called Inert gases.