1. 4.2 A guided tour of the Periodic Table I CAN: -RECOGNIZE THAT ATOMS CAN BECOME CATIONS AND ANIONS BECAUSE THEY GAIN OR LOSE ELECTRONS. -RECOGNIZE THE ATOMIC NUMBER WILL STAY THE SAME AND DUE TO ISOTOPES THE MASS NUMBER CHANGES. -CALCULATE THE ATOMIC NUMBER, MASS NUMBER, CHARGE, AND IDENTITY OF THE ELEMENT BASED ON THE PROTONS, NEUTRONS, AND ELECTRONS

2. What is the purpose of the periodic table?  To organize elements so you can find what you need to know quickly.

3. Organization of the periodic table.  Properties can be predicted based on where the element is located.  Based on # of protons.  hydrogen=1, helium-2, etc.  Periodic Law: repeating chemical and physical properties of elements change periodically with the atomic number of elements.  This meaning will become much clearer soon!

5. The periodic table helps determine electron arrangement  Horizontal rows=periods  Based on number of protons.  Can also determine electrons.  Electron configurations.  Energy level, orbital, number of electrons.  Carbon  1s2  2s2  2p2

6. Elements in the same group have similar properties  Groups: vertical column of elements  Valance electrons determine chemical properties  Elements in same group have some number of valance electrons therefore…

7. Some Atoms for Ions  Why are Group 1 elements reactive?  Atoms that do not have filled outer layers undergo ionization.  Gain or lose electron.  Will no longer have the same number of electrons as protons (charged)  Ion: has lost or gained electron, has positive or negative charge.  Positive ions (lost electron)= cations  Lithium  Negative ions (gained electron)=anions  Fluorine

8. How do Structures of Atoms Differ?  Atomic number (Z): Number of protons  Mass Number (A): the sum of the number of protons and neutrons in the nucleus.  Fluorine has 9 protons and 10 neutrons=?  Oxygen has 8 protons and 8 neutrons=?  Why aren’t electrons included in mass?  Atoms of each element will always have same atomic number, but may have different mass numbers.

9. Isotopes  An atom that has the same number of protons as other atoms of the same element do but that has different number of neutrons.  3 times the mass.

10. Calculating the number of neutrons in an atom  Uranium:  Atomic number=92  Mass Number=235  Number of neutrons: 143

11. The mass of an atom  Fluorine atom has a mass less than one trillionth of a billionth of a gram.  Atomic mass unit (amu): a unit of mass that describes the mass of an atom or molecule; it is exactly one twelfth of the mass of a carbon atom with a mass number of 12.  Average atomic mass: the weighted average of the masses of all naturally occurring isotopes of an element.