Valence electrons are the electrons located in the outermost shell of an atom. Their number fundamentally dictates how an element interacts with others in chemical reactions, as they are involved in forming chemical bonds. Understanding this count allows chemists to predict whether an atom will tend to gain, lose, or share electrons to achieve a stable configuration.
The Direct Answer: Group 16 Elements
The elements that contain six valence electrons belong to Group 16 of the periodic table. This collection is commonly known as the Chalcogens or the oxygen family. The group includes five naturally occurring elements:
- Oxygen (O)
- Sulfur (S)
- Selenium (Se)
- Tellurium (Te)
- Polonium (Po)
Oxygen and Sulfur are the most well-known, playing major roles in biology and industry.
While all Group 16 elements share six valence electrons, their physical properties vary widely. Oxygen is a gas at room temperature, while Sulfur, Selenium, Tellurium, and radioactive Polonium are solids.
Understanding Valence Electrons and the Periodic Table
The periodic table is arranged so that an element’s position immediately reveals its number of valence electrons for the main group elements. For the groups on the right side of the table (Groups 13 through 18), the number of valence electrons is simply the group number minus ten.
This six-electron count is directly reflected in the general valence shell electron configuration for these elements, which is written as \(ns^2np^4\). The letter ‘n’ represents the highest principal energy level, which corresponds to the row the element is in. The superscripts indicate the number of electrons in each subshell, with two electrons in the \(s\) subshell and four electrons in the \(p\) subshell. Adding these superscripts confirms the total of six valence electrons. For example, oxygen’s valence configuration is \(2s^22p^4\), and sulfur’s is \(3s^23p^4\), both summing to six.
Chemical Reactivity and Bonding
The chemical behavior of elements with six valence electrons is governed by their tendency to achieve a stable, full outer shell. This stability is represented by the Octet Rule, which states that atoms are most stable when their outermost shell contains eight electrons. Since Group 16 elements have six, they actively seek two additional electrons to complete their octet.
There are two primary ways these elements satisfy this need. The first is by gaining two electrons from another atom, typically a metal, forming a stable anion with a negative two charge (-2). For instance, oxygen gains two electrons to become the oxide ion (\(O^{2-}\)), and sulfur becomes the sulfide ion (\(S^{2-}\)), both achieving a full octet.
The second method is sharing electrons with other nonmetals through covalent bonding. In this process, the element shares its six valence electrons and the other atom’s electrons to form shared pairs, completing the octet for all atoms involved. A classic example is the formation of a water molecule (\(H_2O\)), where the oxygen atom shares one electron with each of the two hydrogen atoms, forming two covalent bonds.