Valence Electrons and the Periodic Table

The Organic Chemistry Tutor
26 Sept 201711:32
EducationalLearning
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TLDRThis educational video script explains the concept of valence and core electrons in atoms, using nitrogen and aluminum as examples. It demonstrates how to calculate these electron numbers through Bohr models, electron configurations, and periodic table group numbers. The script also highlights the importance of valence electrons in chemical reactions and provides a quick method to determine core electrons, especially for larger atoms like iodine, by using atomic and group numbers.

Takeaways
  • 🔬 Nitrogen has an atomic number of 7 and an average atomic mass of 14.01, with 7 protons and 7 electrons, making it electrically neutral.
  • 🌐 The Bohr model for nitrogen shows 2 electrons in the first shell and 5 in the second shell, with the outermost 5 being valence electrons.
  • 💡 Core electrons are the inner shell electrons that do not participate in chemical reactions, while valence electrons are the outermost and are involved in reactions.
  • 📚 Aluminum, with an atomic number of 13, has 3 valence electrons in its highest energy level and 10 core electrons, totaling 13 electrons.
  • 📝 Electron configurations, such as 1s2 2s2 2p3 for nitrogen and 1s2 2s2 2p6 3s2 3p2 for aluminum, help identify valence and core electrons.
  • 🧩 The periodic table can be used to determine the number of valence electrons based on the group number of representative elements.
  • 🌿 Group 1 elements like hydrogen have 1 valence electron, while group 2 elements like magnesium have 2 valence electrons.
  • 💎 Group 13 elements like aluminum have 3 valence electrons, and group 15 elements like nitrogen have 5 valence electrons.
  • 🌀 Halogens, found in group 17, have 7 valence electrons, but helium, despite being a noble gas, only has 2 valence electrons.
  • 📉 Chlorine, with an atomic number of 17, has an electron configuration of 1s2 2s2 2p6 3s2 3p5, indicating 7 valence electrons and 10 core electrons.
  • 🔢 Iodine, with an atomic number of 53, can have its core electrons quickly determined by subtracting the group number (7 valence electrons) from the atomic number, resulting in 46 core electrons.
Q & A

  • What is the atomic number of nitrogen?

    -The atomic number of nitrogen is 7, which means it has 7 protons and, in a neutral state, 7 electrons.

  • How many valence electrons does nitrogen have?

    -Nitrogen has 5 valence electrons, which are located in the outermost energy level of the atom.

  • What is the electron configuration of nitrogen?

    -The electron configuration of nitrogen is 1s² 2s² 2p³, indicating 2 electrons in the first energy level and 5 in the second, with the 5 being the valence electrons.

  • What is the atomic number of aluminum?

    -Aluminum has an atomic number of 13, indicating it has 13 protons and, in a neutral state, 13 electrons.

  • How many valence electrons does aluminum have?

    -Aluminum has 3 valence electrons, which are in the highest energy level of the atom.

  • What is the electron configuration of aluminum?

    -The electron configuration of aluminum is 1s² 2s² 2p⁶ 3s² 3p², showing 3 valence electrons in the third energy level.

  • How can you identify the number of valence electrons using the periodic table?

    -You can identify the number of valence electrons by looking at the group number of representative elements on the periodic table. For example, elements in group 1 have 1 valence electron, and elements in group 17 (the halogens) have 7 valence electrons.

  • What is the atomic number of chlorine?

    -Chlorine has an atomic number of 17, indicating it has 17 protons and, in a neutral state, 17 electrons.

  • How many valence electrons does chlorine have?

    -Chlorine has 7 valence electrons, which are in the outermost energy level of the atom.

  • What is the electron configuration of chlorine?

    -The electron configuration of chlorine is 1s² 2s² 2p⁶ 3s² 3p⁵, with the 7 electrons in the 3p sublevel being the valence electrons.

  • Why are valence electrons more important in chemical reactions than core electrons?

    -Valence electrons are more important in chemical reactions because they are the outermost electrons and are involved in the formation of chemical bonds, while core electrons are generally not involved in chemical reactions.

  • How can you quickly determine the number of core electrons in a large atom like iodine?

    -You can quickly determine the number of core electrons by subtracting the number of valence electrons (based on the group number) from the total number of electrons (based on the atomic number). For iodine, with an atomic number of 53 and being in group 7A, it has 7 valence electrons, so the number of core electrons is 53 - 7 = 46.

Outlines
00:00
🔬 Understanding Valence and Core Electrons in Atoms

This paragraph introduces the concept of valence and core electrons in atoms using nitrogen and aluminum as examples. Nitrogen, with an atomic number of 7, has 7 electrons, 5 of which are valence electrons in the second energy level, and 2 core electrons. Aluminum, with an atomic number of 13, has 3 valence electrons in its third energy level and 10 core electrons. The paragraph emphasizes the importance of valence electrons in chemical reactions and the neutrality of atoms with equal numbers of protons and electrons, contrasting with ions where this balance differs.

05:01
📚 Electron Configuration and Valence Electron Identification

This section explains how to identify the number of valence and core electrons using electron configurations for nitrogen and aluminum. The electron configuration for nitrogen is given as 1s² 2s² 2p³, indicating 5 valence electrons in the 2p sublevel. For aluminum, the configuration is 1s² 2s² 2p⁶ 3s² 3p², with 3 valence electrons in the 3p sublevel and 10 core electrons. The paragraph also discusses the use of the periodic table to determine valence electrons based on group numbers, providing examples for groups 1, 2, 13, 14, 15, 16, and 17, and noting exceptions like helium and noble gases.

10:02
🧠 Efficiently Determining Core Electrons Using the Periodic Table

The final paragraph focuses on an efficient method to determine the number of core electrons in larger atoms, exemplified by iodine with an atomic number of 53. By using the group number (7a for iodine), which indicates 7 valence electrons, one can calculate the number of core electrons as the total number of electrons minus the valence electrons (53 - 7 = 46 core electrons). This method is highlighted as a time-saving approach for atoms with a higher number of electrons, avoiding the need for detailed Bohr model drawings or lengthy electron configurations.

Mindmap
Keywords
💡Valence Electrons
Valence electrons are the outermost electrons in an atom that are involved in chemical reactions. They are crucial for determining the chemical properties and reactivity of elements. In the video script, valence electrons are identified for nitrogen, aluminum, and chlorine by examining their electron configurations and energy levels, illustrating their role in chemical bonding and reactions.
💡Atomic Number
The atomic number is a unique identifier for each element, representing the number of protons in the nucleus of an atom. It is used to determine the number of electrons in a neutral atom, as seen in the script with nitrogen having an atomic number of 7, which corresponds to 7 electrons.
💡Electron Configuration
Electron configuration refers to the distribution of electrons in an atom's energy levels and sublevels. It is a systematic way to represent the arrangement of electrons and helps in understanding an element's chemical behavior. The script uses electron configurations for nitrogen and aluminum to identify their valence electrons.
💡Core Electrons
Core electrons are the electrons that occupy the lower energy levels or shells within an atom and are not involved in chemical reactions to the same extent as valence electrons. The script distinguishes core electrons from valence electrons, with nitrogen having two core electrons and aluminum having ten.
💡Bohr Model
The Bohr model is a simplified representation of the atom, where electrons orbit the nucleus in discrete energy levels or shells. The script uses a simple Bohr model to illustrate the electron arrangement in nitrogen, helping to visualize the concept of valence and core electrons.
💡Energy Levels
Energy levels, also known as shells, are regions around the nucleus where electrons are most likely to be found. The script discusses the first, second, and third energy levels for nitrogen and aluminum, showing how electrons are distributed across these levels.
💡Sublevels
Sublevels, such as s, p, d, and f, are subdivisions within energy levels that further describe the shape and orientation of electron orbitals. The script mentions s and p sublevels in the context of nitrogen and aluminum's electron configurations.
💡Ions
Ions are atoms or molecules that have a net electric charge due to the loss or gain of electrons. The script notes that the number of protons and electrons differ in ions, which affects the calculation of valence and core electrons.
💡Periodic Table
The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties. The script uses the periodic table to explain how the group number of representative elements can be used to quickly determine the number of valence electrons.
💡Group Number
Group number on the periodic table indicates the number of valence electrons in the outermost shell of an element. The script explains that elements in the same group have the same number of valence electrons, which is used to identify valence electrons for elements like hydrogen, helium, and iodine.
💡Noble Gases
Noble gases are a group of elements in the periodic table that are characterized by their low reactivity due to having a full set of valence electrons. The script mentions helium as a noble gas with two valence electrons, contrasting with other noble gases that have eight valence electrons.
Highlights

The video explains how to calculate valence electrons and understand their significance.

Nitrogen has an atomic number of 7 and an average atomic mass of 14.01, with seven protons and electrons.

A simple Bohr model of nitrogen is drawn to illustrate its electron configuration.

Nitrogen has five valence electrons in the outermost energy level.

Core electrons are the inner shell electrons not involved in chemical reactions.

Aluminum has an atomic number of 13 and an average atomic mass of 26.98.

Aluminum's electron configuration is explained with three valence electrons.

Aluminum has ten core electrons in the first and second energy levels.

Valence electrons are crucial for chemical reactions, unlike core electrons.

Electron configurations for nitrogen and aluminum are provided as examples.

Chlorine's electron configuration is given as 1s2 2s2 2p6 3s2 3p5 with seven valence electrons.

The periodic table can be used to identify the number of valence electrons based on group number.

Elements in group 1 have one valence electron, and group 2 elements have two.

Group 13 elements, including aluminum, have three valence electrons.

Group 5 elements like nitrogen and phosphorus have five valence electrons.

Halogens, such as chlorine, have seven valence electrons.

Iodine, with an atomic number of 53, is used to demonstrate an efficient method to find core electrons.

The total number of electrons equals the sum of core and valence electrons.

Iodine has 46 core electrons, identified by subtracting valence electrons from the atomic number.

Transcripts

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Valence ElectronsElectron ConfigurationChemical ReactionsNitrogen AtomAluminum AtomChlorine AtomPeriodic TableAtomic NumberCore ElectronsEducational Video