Antimony (Sb) is a shiny, silvery-white metalloid element found in Group 15 of the Periodic Table. A metalloid possesses properties intermediate between those of metals and nonmetals. Antimony is primarily used today in alloys to increase hardness and as a component in flame-retardant materials. The neutral Antimony atom, the form most commonly referenced in chemistry, contains a total of 51 electrons.
Calculating the Total Electron Count
The total number of electrons in a neutral atom is determined by the Atomic Number (Z). The atomic number represents the exact count of protons found within the nucleus. Every element is uniquely identified by this number.
Antimony’s atomic number is 51, meaning it has 51 protons in its nucleus. In a neutral atom, the positive charge from the protons must be balanced by the negative charge from the electrons. Therefore, a neutral Antimony atom contains exactly 51 electrons.
Distribution Across Electron Shells
These 51 electrons are organized into specific energy levels, or electron shells. The shells are numbered starting from \(n=1\) closest to the nucleus and moving outward.
The full arrangement of Antimony’s 51 electrons is described using the shell model notation: 2, 8, 18, 18, 5, indicating electrons distributed across five main shells. The innermost shell (\(n=1\)) holds 2 electrons, the second shell (\(n=2\)) holds 8, and the third shell (\(n=3\)) contains 18 electrons.
The fourth shell (\(n=4\)) also accommodates 18 electrons. The remaining 5 electrons reside in the outermost shell, the fifth principal energy level (\(n=5\)). A more detailed representation, the electron configuration, specifies the sub-levels (orbitals) within these shells: \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 4d^{10} 5s^2 5p^3\).
Antimony’s Chemical Behavior and Valence Electrons
The chemical behavior of Antimony is largely governed by the electrons in its outermost shell, known as valence electrons. Antimony has 5 valence electrons, located in the fifth principal energy level (\(n=5\)). Specifically, these 5 electrons occupy the \(5s\) and \(5p\) orbitals, represented as \(5s^2 5p^3\).
The arrangement of these valence electrons dictates how Antimony interacts with other elements. Because it is in Group 15, Antimony can either gain three electrons to achieve a stable octet (resulting in a \(-3\) oxidation state) or lose electrons. It commonly exhibits oxidation states of \(+3\) or \(+5\) in compounds.
The \(+3\) state occurs when Antimony uses only the three \(5p\) electrons for bonding, leaving the pair of \(5s\) electrons non-bonding (the “inert pair effect”). When all five valence electrons are involved in bonding, the element exhibits the \(+5\) oxidation state.