Question

Which elements have only one electron in their highestenergy \(s\) orbital in their ground state?

Short answer

The elements that have only one electron in their highest energy 's' orbital in their ground state are Hydrogen (H), Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr).

Step-by-step solution

Recognize the 's' orbital

An 's' orbital can hold up to 2 electrons. When it has only 1 electron, this is normally in either: Hydrogen, which has only 1 electron, or any of the alkali metals (Group 1 on the periodic table excluding Hydrogen), which have their outermost electron in an 's' orbital.

Identifying elements in ground state with one electron in their highest energy s orbital

These elements are in Group 1 of the periodic table: Hydrogen (H), Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr). Each of these elements has one valence electron in their outermost s orbital.

Formulate the answer

The elements that have only one electron in their highest energy 's' orbital in their ground state are Hydrogen (H), Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr).

Key concepts

s orbital

An 's' orbital is a type of atomic orbital where electrons are found in an atom. It is spherical in shape, which is why it is called 's', standing for 'spherical'. Each 's' orbital can accommodate up to two electrons. However, in the case of hydrogen and alkali metals, the 's' orbital in their outermost shell contains only one electron. This single electron configuration is crucial because it makes these elements highly reactive, especially the alkali metals.
The first 's' orbital appears in the first energy level and is labelled as the 1s orbital. As you move up the energy levels, you encounter 2s, 3s, and so on. Each time an 's' orbital is filled, it signifies a key step in the filling of electron shells around an atom's nucleus, hugging the nucleus most closely among the other types of orbitals, such as 'p', 'd', and 'f' orbitals.
This single electron presence is a hallmark of alkali metals. It influences their chemical properties and reactions, especially in bonding with other elements.

valence electrons

Valence electrons are the electrons located in the outermost shell of an atom. These electrons are vital because they are the ones involved in forming chemical bonds. For elements like alkali metals, the most external electron is in the 's' orbital and is a single valence electron.
The presence of just one valence electron accounts for the high reactivity of alkali metals. They readily lose this lone electron to achieve a stable electron configuration similar to the noble gases, which leads to the formation of positive ions. For example, when interacting with elements like chlorine, alkali metals easily give up their one valence electron to chlorine, forming compounds such as sodium chloride.
Understanding the behavior of valence electrons helps explain why Group 1 elements engage so readily in chemical reactions. They not only determine the reactivity but also influence the type of bonds these elements can form with others.

periodic table

The periodic table is an organized chart of elements that highlights recurring trends in their properties. It is structured in such a way that elements with similar properties are grouped together. One key feature of the periodic table is its division into groups, which are columns of elements sharing similar characteristics.
The alkali metals, including lithium, sodium, and potassium, belong to Group 1 of the periodic table. Each of these elements has one electron in its outermost 's' orbital. Their position within the periodic table reflects their increasing atomic number, reactivity, and the pattern of their valence electrons.
By understanding their placement within the periodic table, one can predict the chemical behavior of these alkali metals. The table not only provides information about atomic numbers and weights but also offers insight into the electronic configuration by detailing the grouping of elements by similar valence electron arrangements, like those seen in the 's' orbital for alkali metals.