For each element, indicate the number of valence electrons, core electrons, and unpaired electrons in the ground state: (c) fluorine.

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Identify the atomic number of fluorine, which is 9, indicating it has 9 electrons.

Determine the electron configuration of fluorine in its ground state: 1s^2 2s^2 2p^5.

Count the valence electrons: Valence electrons are those in the outermost shell. For fluorine, the 2s and 2p orbitals are the outermost, contributing a total of 7 valence electrons (2 from 2s and 5 from 2p).

Count the core electrons: Core electrons are those not in the outermost shell. For fluorine, the 1s orbital contains 2 core electrons.

Determine the number of unpaired electrons: In the 2p orbital, there are 5 electrons. According to Hund's rule, these electrons will fill the three 2p orbitals as follows: one electron in each of the three orbitals, and the remaining two will pair up in two of the orbitals, leaving one unpaired electron.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Valence Electrons

Valence electrons are the outermost electrons of an atom and are crucial for determining how an element will react chemically. For fluorine, which has an atomic number of 9, there are 7 valence electrons in its outer shell (2s² 2p⁵). These electrons are involved in bonding and influence the element's reactivity.

Core Electrons

Core electrons are the electrons that are not involved in bonding and are located in the inner shells of an atom. In the case of fluorine, there are 2 core electrons in the 1s orbital. Understanding the distinction between core and valence electrons is essential for predicting chemical behavior and stability.

Unpaired Electrons

Unpaired electrons are those that occupy an orbital alone and are significant in determining the magnetic properties and reactivity of an atom. For fluorine, there are 1 unpaired electron in the 2p orbital, which contributes to its high reactivity as it seeks to pair with another electron to achieve a stable octet configuration.