1. UNIT 5: THE PERIODIC TABLE

2. Organizing the Elements How would you organize the people in this room? How did chemists begin to organize the known elements?

3. Organizing the Elements

5. The periodic law: When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

6. Organizing the Elements

7. Metals are good conductors of heat and electric current.

8. Organizing the Elements In general, nonmetals are poor conductors of heat and electric current.

9. Organizing the Elements A metalloid generally has properties that are similar to those of metals and nonmetals.

10. Classifying the Elements The elements in groups 1A through 7A are called the representative elements. The group number equals the number of valence electrons in an element in that group. Valence electrons are the electrons in the highest occupied energy level of an atom.

11. Classifying the Elements The elements in Group 1A are called the alkali metals. The elements in Group 2A are called the alkaline earth metals. The elements in Group 7A of the periodic table are called the halogens. The noble gases are the elements in Group 8A of the periodic table.

12. Classifying the Elements The elements in the middle of the periodic table are called the transition metals, or sometimes the Group B elements. The two rows shown at the bottom of the periodic table are called the inner transition metals.

13. Periodic Trends What is the underlying cause of periodic trends? Coulombic attraction: the attraction between oppositely charged particles

14. Periodic Trends What are the trends among the elements for atomic size? In general, atomic size increases from top to bottom within a group and decreases from left to right across a period?

15. Periodic Trends

16. How do ions form? Positive and negative ions form when electrons are transferred between atoms.

17. Periodic Trends How do ions form? Positive and negative ions form when electrons are transferred between atoms.

18. Periodic Trends Some compounds are composed of particles called ions. An ion is an atom or group of atoms that has a positive or negative charge. A cation is an ion with a positive charge. An anion is an ion with a negative charge.

19. Periodic Trends Cations are always smaller than the atoms from which they form. Anions are always larger than the atoms from which they form.

20. Periodic Trends Size generally increases

21. Periodic Trends The energy required to remove an electron from an atom is called ionization energy. First ionization energy tends to decrease from top to bottom within a group and increase from left to right across a period.

22. Periodic Trends

23. Electronegativity is the ability of an atom of an element to attract electrons when the atom is in a compound.