What Element Is Sb

Antimony: What It Actually Is and Why It Keeps Turning Up in Your Work

Sb is antimony, atomic number 51, right between arsenic and tellurium on the periodic table. It's a brittle, silvery-white metalloid that sits in group 15. If you're dealing with it in a lab or industrial setting, you already know it has a reputation for being tricky to work with. It expands when it solidifies, which sounds convenient until you need a precise mold and it pushes everything apart. The melting point is around 630.6 degrees Celsius, and it boils at roughly 1,587 degrees. That's a wide working window, but the oxidation behavior makes everything messier than you'd expect. When people search what element is Sb, they usually want more than the periodic table entry. Antimony is used heavily in flame retardants, predominantly as antimony trioxide in combination with halogenated compounds. It shows up in lead-acid batteries too, where adding a small percentage of antimony to the lead grids improves mechanical strength and charge acceptance. You'll find it in semiconductors as gallium antimonide for infrared detectors. And in metallurgy, it's a hardening agent for lead and a component in certain bearing alloys. The thing most beginners get wrong is assuming antimony behaves like a typical metal. It doesn't. It's a metalloid with a layered crystal structure that gives it perfect cleavage planes, meaning it fractures in a very directional way. I once spent three days trying to machine a small antimony ingot for a custom solder composition test, only to realize the material was shattering along those planes no matter how slow I ran the lathe. The workaround was switching to a cold fracture approach and then sintering the pieces under a controlled atmosphere instead. That cut the process down from two full days to about four hours.

Antimony trioxide is the form you'll encounter most often in safety data sheets and industrial supply catalogs. It's a white powder, slightly soluble in acid, and basically inert in water. The hazard profile is moderate but real. Inhalation of the dust causes respiratory irritation, and chronic exposure has been linked to cardiovascular and respiratory effects. OSHA's PEL is 0.5 milligrams per cubic meter as an eight-hour time-weighted average. That's low enough that standard dust masks aren't always sufficient for prolonged handling, which is something not every hobbyist or small lab operator reads carefully enough before starting a project. Another counter-intuitive detail: antimony tends to segregate during solidification. If you're making an alloy and want uniform distribution, you can't just melt and pour. The element has a strong tendency to form concentration gradients, especially in cast forms. I learned this the hard way when my first batch of antimony-doped lead came back with inconsistent hardness readings across the sample. XRF spot analysis showed the antimony was concentrated near the top of the ingot and nearly absent at the bottom. The fix was mechanical stirring during the melt phase followed by rapid quenching. It didn't solve it completely, but it got the variation down from a factor of three to something manageable within five percent. Here's another nuance that doesn't make it into the general references. Antimony can exist in both +3 and +5 oxidation states, and the +3 state is far more common in environmental and biological contexts. But in certain reducing conditions, like those found in hydrothermal veins, antimony forms complex thioantimonites that are soluble and mobile. This is why antimony contamination around old mining sites is harder to remediate than you'd think. Chelating agents don't always grab it effectively because the sulfur coordination changes the chemistry entirely. I worked on a site remediation project once where the initial plan called for standard phosphate precipitation, which works fine for many heavy metals. It failed for antimony because the pH window for effective precipitation is much narrower than for something like lead or cadmium. We ended up using iron hydroxide co-precipitation adjusted to a pH of around 7.5, which brought the antimony concentration down from 12 micrograms per liter to under 2. That took multiple passes over six weeks.

If you need a source for antimony compounds, Fischer Scientific, Sigma, and Strem are the usual suspects. For elemental antimony, you're better off with specialized metal suppliers because the general chemical distributors tend to stock it in smaller quantities at higher markups. Be aware that the purity grades matter significantly. Technical grade might contain traces of arsenic, gold, silver, or bismuth depending on the ore source, and those impurities can throw off sensitive applications like semiconductor work or precise alloy formulation. If you need high purity, 99.99 percent is the standard benchmark, and you should verify the certificate of analysis rather than assuming what the label says. One final practical note. Antimony fumes are generated when you heat it above its melting point in air, and those fumes are toxic. Always use adequate ventilation when melting or casting. I've seen plenty of people skip this step because they're working with small batches and assume the volume doesn't warrant the setup. It does. Even a few grams of molten antimony in an unventilated space can push airborne concentrations past safe limits within minutes.