The identity of any chemical element is fundamentally determined by the particles located within its atomic nucleus. These subatomic particles are the protons, which carry a positive electrical charge. The number of protons is unique to each element, acting like a chemical fingerprint that distinguishes one type of atom from all others.
Defining Yttrium’s Identity
Yttrium is defined by the fixed count of protons in its atomic nucleus, which is exactly 39. This value is formally known as the atomic number, represented by the symbol \(Z\).
The atomic number \(Z=39\) for Yttrium is an unchangeable property of this element. If an atom were to gain or lose a single proton, its atomic number would shift, and it would cease to be Yttrium, transforming instead into a different element entirely. For example, an atom with 38 protons is Strontium, and one with 40 protons is Zirconium.
The element’s symbol, Y, on the periodic table is directly linked to this proton count. This precise number of protons is what places Yttrium in the fifth period and Group 3 of the periodic table.
The Complete Atomic Structure of Yttrium
While the proton count is fixed, the total structure of the Yttrium atom involves other particles in the nucleus and surrounding it. The nucleus also contains neutrons, which are neutral particles that contribute to the atom’s mass but not its identity. The sum of protons and neutrons gives the mass number (\(A\)), and variations in the neutron count lead to different isotopes of Yttrium.
The most common and naturally occurring form is Yttrium-89 (\(^{89}\text{Y}\)), which has a mass number of 89. Since 39 of those nuclear particles are protons, the most stable isotope of Yttrium contains 50 neutrons in its nucleus (\(89 – 39 = 50\)). Yttrium-89 is the only stable isotope of the element, making up 100% of the naturally found Yttrium.
In a neutral Yttrium atom, the number of electrons orbiting the nucleus is equal to the number of protons, meaning it has 39 electrons. These electrons are arranged in shells, with the outermost shell containing the valence electrons that govern how Yttrium interacts with other elements. Yttrium tends to lose three of its outer electrons during chemical reactions, establishing its primary chemical behavior.