1. Periodic Table Families Kelley Kuhn Center for Creative Arts

2. –The periodic table is made up of both rows and columns of elements. –Each element is identified by its chemical symbol. –The number above the symbol is the atomic number –The number below the symbol is the average atomic weight of the element. –A row is more formally called a period –A column is more formally called a group Welcome to the Periodic Table!!!

3. (A) Groups of the periodic table, and (B) periods of the periodic table.

4. Periodic Table and Electron Configurations Note the patterns of the electron configurations in both the periods and columns. Elements in same column will have the same outer shell electron configuration.

5. –Each period ends with a completely filled outer shell that has the maximum number of electrons for that shell (the noble gases). –The number identifying the A families identifies the number of electrons in the outer shell, except helium. –The outer shell electrons (aka valence shell electrons) are responsible for chemical reactions of elements and the ions they form. –Group A elements are called representative elements –Group B elements are called transition elements.

6. Metal: Elements that are conductors, shiny, hard, malleable, ductile, and are found to the left of the stair step line on the table. Most elements are metals. Non-Metal: Elements in the upper right corner of the periodic table that are insulators, brittle, and dull. Their chemical and physical properties vary greatly from metals. Metalloid: Elements that lie on a stair step line between the metals and non-metals. They are semi- conductors with chemical and physical properties that are intermediate between the others. Elements on the periodic table can be grouped in different ways.

7. Dmitri Medeleev gave us a functional method by which to classify and organize the elements. –Mendeleev’s scheme was based on chemical properties of the elements. –He noticed that the chemical properties of elements reoccurred in a periodic manner which led to the idea of the Periodic Law which states that similar physical and chemical properties recur periodically when the elements are listed in order of increasing atomic number. –The “periodicity” of the elements was demonstrated by Medeleev when he used the table to predict the occurrence and chemical properties of elements which had not yet been discovered. So, how did the elements get organized this way?

8. Mendeleev left open spaces in his table when the properties of the elements above and below did not seem to match. He predicted the existence of unknown elements on the basis of these blank spaces. When the unknown elements were discovered, it was found that Mendeleev had closely predicted the properties of these elements as well as where they would be discovered.

9. Periodic Properties Periodic law = when elements are arranged by atomic number, their physical and chemical properties vary periodically. We will study the following periodic trends: –Atomic radii –Ionization energy –Electron affinity

10. Atomic Radius/Atomic Size Sizes of the atoms decrease as we move from left to right across a period This is due to the increasing number of protons in the nucleus, so the electrical attraction between the nucleus and the orbiting electrons gets stronger and pulls the electrons closer to the nucleus. As you move down a group, the sizes of the atoms increase due to the addition of additional electron orbitals.

11. Atomic Size based on radius

12. Predict the order of the following elements, from smallest atomic radius to greatest, based on their position on the periodic table. Ba, Ca, Na, K B, Li, F, Cd, Fe Predict:

13. ELECTRON AFFINITY Electron Affinity, E, is a reflection of how easily an atom in the gaseous state will gain an electron. It is a measure of how much energy is released when this occurs. More energy = higher electron affinity As you can see, the halogens (group VIIA) clearly have a strong tendency to gain an electron/become negatively charged based on their large E values. The alkali metals (group IA) elements have a very small E ea so they do not easily gain electrons.

14. Electron Affinity So, to sum up: Electron affinity _____________ across a period. Electron affinity _____________ down a group/family.

15. Predict: Predict the order of the following elements, from smallest electron affinity to greatest, based on their position on the periodic table. Si, Mo, Ti, Na B, P, Cl, Ga

16. Ionization Energy: Periodic table Ionization Energy vs atomic # Ionization energy reflects how easily an atom will lose an electron. Lower energy = more likely to lose electron.

17. Ionization energy…. So, to sum up: Ionization energy _____________ across a period. Ionization energy _____________ down a group/family.

18. Predict Predict the order of the following elements, from smallest ionization energy to greatest, based on their position on the periodic table. Si, Mo, Ti, Na B, P, Cl, Ga

19. –Most atoms are NOT stable in their atomic form. –In order to achieve stability, they gain or lose electrons to reach noble gas electron configuration (EC). –When an atom or molecule gain or loses an electron it becomes an ion. A cation has lost an electron and therefore has a positive charge An anion has gained an electron and therefore has a negative charge. How do atoms achieve stability?

20. –Elements with 1, 2, or 3 electrons in their outer shell tend to lose electrons to fill their outer shell and become cations. These are the metals which always tend to lose electrons. This helps them attain noble gas EC. –Elements with 5 to 7 electrons in their outer shell tend to gain electrons to fill their outer shell and become anions. These are the nonmetals which always tend to gain electrons. Once again, this gives them noble gas EC. –Semiconductors (metalloids) occur at the dividing line between metals and nonmetals and can either gain or lose electrons. FYI: How can I predict the ions that form from various elements?

21. Predict: What ions will form from: Ca? K? Cl? B? O? S?