Ch.9 - Periodic Properties of the Elements

Tro - Chemistry: A Molecular Approach 5th Edition

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Tro 5th Edition

Ch.9 - Periodic Properties of the Elements

Problem 45a

Chapter 9, Problem 45a

Use the periodic table to determine each quantity. a. the number of 2s electrons in Li

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Identify the electron configuration of lithium (Li).

Recall that lithium has an atomic number of 3, which means it has 3 electrons.

Write the electron configuration for lithium: 1s² 2s¹.

Determine the number of electrons in the 2s subshell from the electron configuration.

Conclude that the number of 2s electrons in lithium is 1.

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Key Concepts

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

Periodic Table

The periodic table is a systematic arrangement of elements based on their atomic number, electron configuration, and recurring chemical properties. It provides essential information about each element, including its position, which helps in understanding its electron structure and reactivity. Elements are organized into periods and groups, with similar properties found in the same columns.

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. It follows the Aufbau principle, which states that electrons fill the lowest energy orbitals first. For lithium (Li), with an atomic number of 3, the electron configuration is 1s² 2s¹, indicating that it has two electrons in the 1s orbital and one in the 2s orbital.

Valence Electrons

Valence electrons are the electrons in the outermost shell of an atom and are crucial for determining an element's chemical properties and reactivity. In the case of lithium, the 2s electron is a valence electron, which plays a significant role in bonding and chemical reactions. Understanding the number of valence electrons helps predict how an element will interact with others.

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