Elements in the S-Block & P-Block of the Periodic Table

S and P Shells

• The electrons that orbit atoms form distinct structures called shells. Each shell contains orbitals, which the electrons occupy according to principles of quantum mechanics. The S-shells have a spherical shape, and multiple S-shells form concentric, onion-like layers, growing outward as you move down the rows in the periodic table. The P-shells have more complex shapes, resembling pressed spheres and mushroom caps.

Alkali Metals and Alkaline Earths

• The first column in the periodic table includes hydrogen and the alkali metals. These elements have one electron in their outermost S-orbital. Though hydrogen fits in this column, it is an oddball element, being the only one in this group that is a gas at normal temperatures. The other alkali metals, lithium through francium, are reactive with water to the point of being nearly explosive. The alkaline earths, which include beryllium through radium, have their outermost s-orbital filled with two electrons. These metals are silvery in color. Some of them, such as calcium and magnesium, are essential to life; others, like beryllium and radium, are toxic.

Noble Gases and Halogens

• The noble gases take up the last column in the periodic table, having their outermost P-orbitals filled. Though helium is a noble gas, it has no P-orbitals and is not part of the P-block. The gases neon through radon are largely unreactive, not even bonding with each other. On the other hand, their next-door neighbors, the halogens, are highly reactive elements. These elements need only one electron to complete their outer P-orbital, and they get them aggressively from other reactive elements that have electrons to spare. Fluorine and chlorine are gases under normal conditions. Bromine is a liquid, and iodine and astatine are solids.

Metalloids and Metals

• Many P-block solids do not quite qualify as metals: they have some luster and conduct heat and electricity poorly to moderately well, but are not ductile. Some, such as silicon, germanium and arsenic, are widely used in electronic components. Other P-block elements, such as aluminum, gallium and indium, are more fully metallic. Aluminum is a common metal with thousands of uses, from aircraft parts to cooking foil; gallium and indium are somewhat more exotic and have low melting points. Electronic parts such as light-emitting diodes use both gallium and indium.