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Ch.9 - Periodic Properties of the Elements
Chapter 9, Problem 43b

Use the periodic table to write an electron configuration for each element. Represent core electrons with the symbol of the previous noble gas in brackets. b. As

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Identify the atomic number of arsenic (As) from the periodic table, which is 33.
Determine the previous noble gas before arsenic, which is argon (Ar) with an atomic number of 18.
Write the electron configuration starting with the noble gas core: [Ar].
Continue the electron configuration from argon by adding electrons to the 4s, 3d, and 4p orbitals: 4s^2, 3d^10, 4p^3.
Combine the noble gas core and the additional electrons to complete the electron configuration: [Ar] 4s^2 3d^10 4p^3.

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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. It is typically written in a specific format that indicates the energy levels and sublevels occupied by electrons. For example, the configuration for an element like Argon (Ar) is 1s² 2s² 2p⁶ 3s² 3p⁶, showing how electrons fill the available orbitals according to the Aufbau principle.
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Noble Gas Notation

Noble gas notation is a shorthand method for writing electron configurations by using the symbol of the nearest preceding noble gas to represent core electrons. This simplifies the notation by focusing on the valence electrons, which are crucial for determining an element's chemical properties. For instance, for Arsenic (As), the configuration can be written as [Ar] 4s² 3d¹⁰ 4p³.
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Periodic Table and Electron Configuration

The periodic table organizes elements based on their atomic number and electron configurations, reflecting periodic trends in chemical properties. Elements in the same group typically have similar valence electron configurations, which influences their reactivity and bonding behavior. Understanding the layout of the periodic table helps predict the electron configuration of elements like Arsenic based on its position.
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