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Exploring Periodic Trends in the Elements: From Mendeleev to the Modern Table

This chapter delves into the evolution of the Periodic Table, starting with Mendeleev's organizing principle based on atomic mass and properties. It then explores Moseley's atomic number concept and the modern table's arrangement by atomic number. The chapter also covers the classification of elements into groups like Alkali Metals and Noble Gases, and discusses the properties of metals, nonmetals, and metalloids. Moreover, it examines key periodic trends including atomic radius, ionization energy, electron affinity, and electronegativity, and explains the Octet Rule and why Noble Gases are unreactive.

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Exploring Periodic Trends in the Elements: From Mendeleev to the Modern Table

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  1. Chapter 5 Periodic Trends

  2. Dimitri Mendeleev • Organized first Periodic Table • Based on increasing atomic mass and properties • Left gaps for non-discovered elements

  3. Moseley • Concept of atomic number • Atomic number= number of protons

  4. Periodic Law • When elements are arranged in increasing atomic number their physical and chemical properties show a pattern

  5. Modern Periodic Table • Based on Atomic number and properties

  6. Group1- Alkali Metals • Group 2- Alkaline Earth Metals • Group 17- Halogens • Group 18- Noble Gases

  7. Lanthanide Series • Actinide Series

  8. Metals • Luster or shine • Conductors • Solids (usually) • Malleable (can be pounded) • Ductile (can be drawn into wires)

  9. Nonmetals • Poor conductors • Most are gases • Variation of physical properties

  10. Metalloids • Semi-metals • Properties of metals and nonmetals

  11. Periodic Trends • Properties of elements can be predicted (trend)

  12. Atomic Radius • Size of the radius of the atom • Across the period- • Down the Group

  13. Examples

  14. Ionic Radius • Size of the ion compared to the neutral atom

  15. Positive ions are smaller than neutral ions • More protons than electrons greater attraction

  16. Negative ions are larger than neutral ions • More electrons than protons less attraction

  17. Ionization Energy • Energy needed to remove an electron • High I.E.  strong attraction • Low I.E.  weak attraction

  18. Across the period: • Down the group:

  19. Successive ionization energies • Energy increase with each electron removed from an atom, but a jump will occur when the valence electrons are all removed

  20. examples

  21. Electron Affinity • Energy change that occurs when an atom gains an extra electron. • Atoms that have a greater attraction for electrons have a more negative affinity

  22. examples

  23. Electronegativity • Ability to attract an electron

  24. Fluorine is the most attractive. • Fluorine’s electronegativity was assigned 4.0 • All elements are compared to Fluorine

  25. Across the Period • Down the Group

  26. Octet Rule • Atoms tend to gain, lose or share electrons in order to acquire an octet. • Metals: gain or lose electrons? • Nonmetals: gain or lose electrons?

  27. Can Hydrogen ever acquire an octet? • Why are Noble Gases unreactive?

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