Antimony (Sb), derived from the ancient Latin name stibium, is classified as a metalloid. This element has been used by humans for millennia, powdered for cosmetics like kohl and various medicines. Today, antimony is a technologically important material, serving as a dopant in semiconductor devices and an additive in flame-retardant materials for plastics and textiles. Its primary modern use is in alloys with lead, increasing hardness and durability for applications like car batteries, bearings, and solders. Understanding the neutron count requires examining its atomic structure.
Decoding Atomic Structure
Every atom is composed of protons, neutrons, and electrons. The nucleus, the dense center of the atom, contains protons and neutrons, while electrons orbit the core. The identity of any chemical element is defined by the number of protons in its nucleus, known as the atomic number (\(Z\)).
The total mass of the nucleus is determined by the sum of protons and neutrons, called the mass number (\(A\)). Because the number of protons (\(Z\)) identifies the element, the number of neutrons (\(N\)) is determined by subtracting the atomic number from the mass number. This relationship is expressed by the formula: Neutrons (N) = Mass Number (A) – Atomic Number (Z).
Antimony’s Naturally Occurring Forms
While the atomic number is fixed for any given element, the number of neutrons can vary among atoms of the same element. Atoms of an element that have the same number of protons but different numbers of neutrons are called isotopes. Antimony’s atomic number (\(Z\)) is 51, meaning every antimony atom has exactly 51 protons.
Antimony exists naturally on Earth as a mixture of two stable isotopes. These two forms are Antimony-121 (\(^{121}\text{Sb}\)) and Antimony-123 (\(^{123}\text{Sb}\)), distinguished by their different mass numbers. Antimony-121 is the more abundant form, making up approximately 57.21% of all naturally occurring antimony atoms. The remaining portion is Antimony-123, which accounts for about 42.79% of the total. The existence of these two stable forms means that antimony does not have a single, fixed number of neutrons.
Calculating Neutron Count
The calculation for the neutron count is a direct application of the formula Neutrons (N) = Mass Number (A) – Atomic Number (Z). For all isotopes of antimony, the atomic number (\(Z\)) is 51.
For the most common isotope, Antimony-121, the calculation is \(121 – 51\). This results in a neutron count of 70 for the \(^{121}\text{Sb}\) isotope.
For the second stable isotope, Antimony-123, the calculation is \(123 – 51\). This shows that the \(^{123}\text{Sb}\) isotope contains 72 neutrons. Therefore, the answer depends on which specific isotope is being examined: 70 or 72.