2. Periodic Law History of the Periodic Table Periodic Trends

3. Mendeleev - 1869 Organize elements according to properties Organize elements according to properties He noticed that certain properties appeared at regular intervals He noticed that certain properties appeared at regular intervals He left empty spots in his table – he predicted that there were elements that scientists did not yet know about He left empty spots in his table – he predicted that there were elements that scientists did not yet know about

4. Mendeleev’s Periodic Table Dmitri Mendeleev

5. Chinese Periodic Table

6. Stowe Periodic Table

7. Moseley - 1913 Slightly changed Mendeleev’s table Slightly changed Mendeleev’s table Ordered elements according to Atomic Number Ordered elements according to Atomic Number Periodic Law = physical and chemical properties of the elements are periodic functions of their atomic numbers Periodic Law = physical and chemical properties of the elements are periodic functions of their atomic numbers

8. Modern Periodic Table Arranged according to Atomic Number Arranged according to Atomic Number Elements with similar properties fall in the same column (group) Elements with similar properties fall in the same column (group) Know these four families: Know these four families: –Noble Gases –Halogens –Alkali Earth Metals –Earth Metals

9. Families of the Periodic Table Noble Gases = Group 18, Unreactive Noble Gases = Group 18, Unreactive Halogens = Group 17, Very reactive Halogens = Group 17, Very reactive Alkali Metals = Group 1, Very reactive Alkali Metals = Group 1, Very reactive Alkaline Earth Metals = Group 2, very reactive Alkaline Earth Metals = Group 2, very reactive

10. Regions of the Periodic Table Metals – to the left of the stair step line Metals – to the left of the stair step line Nonmetals – to the right of the stair step line Nonmetals – to the right of the stair step line Metalloids – Elements that border the stair step line (except for Al) Metalloids – Elements that border the stair step line (except for Al) Transition metals – d block Transition metals – d block Main group elements – s and p block Main group elements – s and p block

11. Periodic Trends – Atomic Radii Atomic Radii – size of the atom, half the distance between the nuclei of identical atoms that are bonded together Atomic Radii – size of the atom, half the distance between the nuclei of identical atoms that are bonded together Across a period – atomic radii decreases due to an increase in the effective nuclear charge Across a period – atomic radii decreases due to an increase in the effective nuclear charge Down a group – atomic radii increases due to addition of outermost electrons to higher energy levels Down a group – atomic radii increases due to addition of outermost electrons to higher energy levels

12. Atomic Radius Atomic Radius Trends in Atomic Radius Li Ar Ne K Na

13. Table of Atomic Radii

14. Periodic Trend – Ionization Energy Ionization energy (IE) – the amount of energy it takes to remove an electron from a neutral atom Ionization energy (IE) – the amount of energy it takes to remove an electron from a neutral atom Ion – formed when at atom loses or gains electrons Ion – formed when at atom loses or gains electrons Ionization – the process that results in the formation of an ion Ionization – the process that results in the formation of an ion

15. Ionization energy increases across a row. Ionization energy increases across a row. –It becomes more difficult to lose valence electrons as you move across a row due to increasing effective nuclear charge. Ionization energy decreases down a group. Ionization energy decreases down a group. –It becomes easier to remove valence electrons as you move down a group because the electrons are farther from the nucleus. Shielding Effect – the inner shell electrons interfere with the nucleus attraction to the valence electrons. Shielding Effect – the inner shell electrons interfere with the nucleus attraction to the valence electrons.

16. First Ionization Energy First Ionization Energy Trends in Ionization Energy K Na Li Ar Ne He

17. First Ionization Energy First Ionization Energy –Increases UP and to the RIGHT E. Ionization Energy

18. Electron Affinity Electron Affinity (EA) - the energy change that occurs when an electron is acquired by a neutral atom Electron Affinity (EA) - the energy change that occurs when an electron is acquired by a neutral atom When an atom gains an electron easily, a large amount of energy is released (indicated by a high negative number). These elements will have a high electron affinity. When an atom gains an electron easily, a large amount of energy is released (indicated by a high negative number). These elements will have a high electron affinity.

19. Electron Affinity - Trend In general, electron affinity increases across a period In general, electron affinity increases across a period –Atoms accept electrons easily. In general, electron affinity decreases down a group. In general, electron affinity decreases down a group. –Larger atoms cannot accept electrons as easily.

20. Electron Affinities of the Elements

22. Why gain or lose electrons? The noble gases are stable because they have 8 electrons in their highest energy level – a complete octet. The noble gases are stable because they have 8 electrons in their highest energy level – a complete octet. The other families need to gain or lose electrons so they can also have a complete octet. The other families need to gain or lose electrons so they can also have a complete octet. Groups 1, 2, 3 lose valence electrons to form cations – positive ions (cations). Groups 1, 2, 3 lose valence electrons to form cations – positive ions (cations). Groups 5, 6, 7 gain electrons to form anions – negative ions (anions). Groups 5, 6, 7 gain electrons to form anions – negative ions (anions).

23. Cations Cations lose valence electrons and become positive. Cations lose valence electrons and become positive. To name a cation, add the word ion to the end of the element name. To name a cation, add the word ion to the end of the element name. Cations are smaller than the original atom. Cations are smaller than the original atom.

24. Anions Anions gain valence electrons and become negative. Anions gain valence electrons and become negative. To name an anion, change the ending of the element name to To name an anion, change the ending of the element name to –ide and add the word ion. Anions are larger than the original atom. Anions are larger than the original atom. Teachers: have students label periodic table Teachers: have students label periodic table

25. Electronegativity Measure of the ability of an atom in a chemical compound to attract electrons. Measure of the ability of an atom in a chemical compound to attract electrons. Fluorine is the most electronegative element and has been assigned an electronegativity value of 4. Fluorine is the most electronegative element and has been assigned an electronegativity value of 4.

26. Electronegativity – Periodic Trends Across a period, electronegativity increases. Across a period, electronegativity increases. –The halogens highly attract electrons. Down a group, electronegativity decreases. Down a group, electronegativity decreases. –Larger atoms do not attract electrons as easily.

27. Periodic Table of Electronegativities

28. Summation of Periodic Trends