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

Valence Electrons of Elements (Simplified)

GOB Chemistry

2. Atoms and the Periodic Table

Valence Electrons of Elements (Simplified)

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2:01 minutes

Problem 72d

Textbook Question

Complete each of the statements a to d using 1, 2, or 3:
1. decreases
2. increases
3. remains the same
Going from left to right across Period 4,
d. the number of valence electrons ________

Verified step by step guidance

Understand the periodic table layout: Period 4 refers to the fourth row of the periodic table, which includes elements from potassium (K) to krypton (Kr).

Recall the concept of valence electrons: Valence electrons are the outermost electrons of an atom and determine its chemical properties. For main group elements, the number of valence electrons corresponds to the group number (1A to 8A).

Analyze the trend across a period: As you move from left to right across a period, the number of valence electrons increases by one for each successive element in the main group elements.

Apply this trend to Period 4: Starting with potassium (K) in Group 1A, which has 1 valence electron, and ending with krypton (Kr) in Group 8A, which has 8 valence electrons, the number of valence electrons increases across the period.

Conclude that the correct answer for part d is '2. increases,' as the number of valence electrons increases from left to right across Period 4.

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Key Concepts

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

Periodic Trends

Periodic trends refer to the predictable patterns observed in the properties of elements as you move across a period or down a group in the periodic table. These trends include atomic radius, ionization energy, electronegativity, and the number of valence electrons, which help in understanding how elements behave chemically.

Valence Electrons

Valence electrons are the electrons located in the outermost shell of an atom and are crucial for determining an element's chemical properties and reactivity. The number of valence electrons influences how an element bonds with others, and in Period 4, elements typically have a consistent increase in valence electrons as you move from left to right.

Period 4 Elements

Period 4 of the periodic table includes elements from potassium (K) to krypton (Kr). As you progress across this period, the atomic number increases, leading to an increase in the number of protons and electrons, which directly affects the number of valence electrons, typically increasing from 1 to 8.

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