Table of contents

1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

2. Atoms and the Periodic Table

Periodic Table: Element Symbols

GOB Chemistry

2. Atoms and the Periodic Table

Periodic Table: Element Symbols

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4:25 minutes

Problem 51

Textbook Question

Why does the fourth period in the periodic table contain 18 elements?

Verified step by step guidance

Understand the structure of the periodic table: The periodic table is organized based on the electron configuration of elements, which determines their chemical properties. Each period corresponds to the filling of a specific set of electron orbitals.

Recall the Aufbau principle: Electrons fill orbitals in order of increasing energy levels. The fourth period involves the filling of the 4s, 3d, and 4p orbitals.

Analyze the orbitals involved: The 4s orbital can hold 2 electrons, the 3d orbital can hold 10 electrons, and the 4p orbital can hold 6 electrons. Adding these together gives a total of 18 electrons.

Relate the electron configuration to the periodic table: Each element in the fourth period corresponds to the addition of one electron to these orbitals, starting with the 4s orbital, then the 3d orbital, and finally the 4p orbital.

Conclude why there are 18 elements: The fourth period contains 18 elements because it includes all the elements whose electrons fill the 4s, 3d, and 4p orbitals, resulting in a total of 18 positions in the period.

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Key Concepts

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

Periodic Table Structure

The periodic table is organized by increasing atomic number and groups elements with similar properties. Each period corresponds to the filling of electron shells, with the fourth period beginning when the 4s subshell is filled, followed by the 3d subshell. This structure helps explain the number of elements in each period.

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. In the fourth period, electrons fill the 4s and 3d orbitals, allowing for a total of 18 electrons (2 in 4s and 10 in 3d, plus 6 in 4p). This configuration is crucial for understanding the number of elements present in this period.

Transition Metals

The fourth period includes transition metals, which are characterized by the presence of d electrons. These elements exhibit unique properties due to their electron configurations, contributing to the total count of 18 elements in this period. Transition metals play a significant role in various chemical reactions and applications.