History of the Periodic Table

1. What did Cannizzaro Do? Developing a method that led to the determination of standard relative atomic masses, which allowed chemists to search for periodic trends among elements History of the Periodic Table

2. What did Mendeleev do? Discovered the periodic law Organized the elements according to increasing atomic mass and noticed that similar properties appeared periodically. What is the periodic law? The physical and chemical properties of the elements are periodic functions of their atomic numbers Demostrated in the periodic table because groups have similar chemical and physical properties and behavior

3. Discovered that nuclear charge(atomic number) not atomic mass, should be the basis for organizing the periodic table What did Mosley do?

4. How do the electron configuration within the same group compare? The configurations of the outermost electron shells of elements within the same group are the same. There are a number of exceptions to this rule, in the transition elements

5. What determines the length of each period in the periodic table? The length of a period is determined by the total number of electrons that can fill the outer sublevel of the elements of that period

6. What is the relationship between the electron configuration of an element and the periods in which that element appears in the periodic table An element’s period corresponds to its highest occupied main energy level.

7. What information is provided by the specific location of an element? The type of sublevel being filled in successive elements of that block S block: groups 1 and 2 P block: groups 13-18 except He(s) D block: groups 3-12 F block: lanthanide and actinide series

8. What are properties of the Group 1: Alkali Metals? • Extremely reactive • react vigorously with water • Silvery in color • Soft enough to be cut with a knife • All have 1 valence electron

9. What are the properties of Group 2: Alkaline earth metals • Less reactive than group 1 elements • Harder, denser, stronger than group 1 • Higher melting points than group 1 • 2 valence electrons

10. What type of elements make up the P block of the periodic table? Nonmetals at the right Metalloids on the stairs Metals under the stairs: these metals are generally ahrder and more dense than the s block metals but softer and less dense than the d-block metals

11. What are properties of the Group 17:halogens? Most reactive nonmetals Fluorine is the most reactive of all nonmetals React vigorously with most metals to form salts Most electronegative elements.

12. What are the properties of the metalloids? B, Si, Ge, As, Sb,Te Mostly brittle solids with electrical conductivities intermediate between those of metals (good conductors) and nonmetals (poor conductors)

13. What are the main group elements and what trends can be seen across periods of these groups s and p group elements Decrease in atomic size Increase in ionization energy Increase in electron affinity Decrease in cationic size Decrease in anionic size Increase in electronegativity

14. What is ion?A charged atom or a charged group of bonded atoms What is ionization? Any process that results in the formation of bonded atoms What is first ionization energy? The energy required to remove one electron from a neutral atom of an element. What is second ionization energy? The energy required to remove an electron from a 1+ ion.

15. How do the first ionization energies of main group elements vary across a period and down a group? Increase across a period and decrease down a group. Across a period, the increasing nuclear charge more strongly attracts electrons in the same energy level and makes them more difficult to remove Down a group, the electrons to be removed from each successive element are in increasingly higher energy levels farther from the nucleus and are more easily removed

16. What is electron affinity? The energy taken in or given off when an electron is added to an atom Electron affinity values are either negative or positive. A negative sign shows that energy is given off and a positive sign show energy is taken in

17. What is the difference between a cation and an anion Cation: positive ion and a metal Anion: negative ion and a nonmetal Cations are always smaller than the atoms they came from Anions are always larger than the atoms they came from