Elements are classified as metals, nonmetals or metalloids. Noble gases are classified separately, although they are sometimes grouped with non-metals despite having different properties.
The majority of elements in the periodic table are classified as metals. Metals have between one and three electrons in their outer shell and readily lose valence electrons. On a periodic table, they are found at the center and left. They are good conductors of heat and electricity, tend to remain solid at room temperature, except for mercury, and have a shiny luster. Most metals are also malleable and ductile.
Non-metals, excluding inert gases, tend to gain electrons. They are placed at the top and right of the periodic table. Unlike metals, non-metals are poor conductors of heat and electricity and most of them are gases at room temperature. However, some are liquids and a few are solids.
Metalloids blur the lines between metals and non-metals. Physically they resemble non-metals but, under some conditions, a few metalloids like silicon, can conduct electricity. Metalloids play an important role in the semiconductor industry.
Located at the far right of the periodic table, inert gases neither lose nor gain electrons. Because they do not react with most substances, these elemental noble gases are useful in applications where reactions are undesirable.