You have cracked a secret code that uses elemental symbols to spell words. The code uses numbers to designate the elemental symbols. Each number is the sum of the atomic number and the highest principal quantum number of the highest occupied orbital of the element whose symbol is to be used. The message may be written forward or backward. Decode the following messages: a. 10, 12, 58, 11, 7, 44, 63, 66
Ch.9 - Periodic Properties of the Elements
Chapter 9, Problem 113
Consider the elements: B, C, N, O, F. d. Which element has three unpaired electrons?

1
Identify the electron configuration of each element in their ground state. The elements given are B (Boron), C (Carbon), N (Nitrogen), O (Oxygen), and F (Fluorine).
Write out the electron configurations using the Aufbau principle, Hund's rule, and the Pauli exclusion principle. Focus on the arrangement of electrons in the outermost shell, particularly the p-orbitals.
Count the number of unpaired electrons in the p-orbitals for each element. Unpaired electrons are those that do not have a paired electron with opposite spin in the same orbital.
Compare the number of unpaired electrons for each element. The element with exactly three unpaired electrons in its p-orbitals is the one you are looking for.
Verify that the element with three unpaired electrons aligns with the general trend in electron configuration across the period in the periodic table.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Electron Configuration
Electron configuration describes the distribution of electrons in an atom's orbitals. Each element has a unique electron configuration that determines its chemical properties. Understanding how to write and interpret these configurations is essential for identifying the number of unpaired electrons in an atom.
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Unpaired Electrons
Unpaired electrons are those that occupy an orbital alone, without a paired electron of opposite spin. The presence of unpaired electrons is crucial for determining an element's magnetic properties and its reactivity. Elements with unpaired electrons tend to be more reactive and are often involved in bonding.
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Valence Electrons
Valence electrons are the outermost electrons of an atom and are involved in chemical bonding. The number of valence electrons can influence how an element interacts with others. For the elements in the question, knowing the number of valence electrons helps in determining how many are unpaired, which is key to answering the question.
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