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Ch.6 - Electronic Structure of Atoms
Chapter 6, Problem 74c

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

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Identify the atomic number of chlorine, which is 17, indicating it has 17 electrons.
Determine the electron configuration of chlorine: start filling the orbitals in order of increasing energy (1s, 2s, 2p, 3s, 3p).
Write the electron configuration for chlorine: \(1s^2 2s^2 2p^6 3s^2 3p^5\).
Identify the valence electrons: the electrons in the outermost shell (3s and 3p orbitals), which total 7 valence electrons.
Determine the number of unpaired electrons: in the 3p orbital, there are 5 electrons, with 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 chlorine, which is in group 17 of the periodic table, there are seven valence electrons. These electrons are involved in forming bonds with other atoms, influencing the element's reactivity and bonding behavior.
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Core Electrons

Core electrons are the electrons that are not involved in bonding and are located in the inner shells of an atom. They are typically shielded from the effects of external electric fields and do not participate in chemical reactions. In chlorine, there are 10 core electrons, which are found in the inner electron shells, providing stability to the atom.
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Unpaired Electrons

Unpaired electrons are those that occupy an orbital alone rather than in pairs. They play a significant role in determining the magnetic properties of an atom and its ability to form bonds. In the case of chlorine, there are three unpaired electrons in its ground state configuration, which contributes to its high reactivity and tendency to form covalent bonds.
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