In the periodic table, elements generally become more metallic down a group. However, elements tend to be less metallic across a period.
Each element in the periodic table is represented by an atomic symbol, atomic number and atomic weight. These elements are organized from left to right in increasing atomic numbers. The horizontal rows of elements are referred to as periods while the vertical columns are called families or groups.
The elements belonging to the same group exhibit similar atomic properties. One method of labeling the various groups is to designate the numbers one to 18 from left to right. Certain groups have specific names to distinguish them from other groups. The elements in group one, except hydrogen, are referred to as the alkali metals while those in group two are called the alkaline-earth metals. The elements belonging to group 17 are the halogens while those in group 18 are known as the noble gases. Elements are also categorized as metals or non-metals.
Elements exhibit periodic trends or patterns. These patterns characterize the nature of the elements within a group or period. Some of the major trends include metallic character, ionization energy and atomic radius. Metallic character pertains to the degree of reactivity of an element, which corresponds to how easily it loses an electron. When going down a group, metallic properties tend to increase, which is a direct result of increasing atomic sizes.