1. Structure of the Atom There are two regions The nucleus With protons and neutrons –Positive charge –Almost all the mass Electron cloud –Most of the volume of an atom –The region where the electron can be found

2. Size of an atom Atoms are incredibly tiny. Measured in picometers (10 -12 meters) –Hydrogen atom, 32 pm radius Nucleus tiny compared to atom –Radius of the nucleus near 10 -15 m. –Density near 10 14 g/cm 3 IF the atom was the size of a stadium, the nucleus would be the size of a marble. California WEB

3. Subatomic particles Electron Proton Neutron NameSymbolCharge Relative mass Actual mass (g) e-e- p+p+ nono +1 0 1/1840 1 1 9.11 x 10 -28 1.67 x 10 -24

4. The Atomic Scale  Most of the mass of the atom is in the nucleus (protons and neutrons) 99%  Electrons are found outside of the nucleus (the electron cloud)  Most of the volume of the atom is empty space “q” is a particle called a “quark”

6. A. Mass Number mass # = protons + neutrons always a whole number NOT a whole number on the Periodic Table! © Addison-Wesley Publishing Company, Inc. weighted average of all isotopes rounded to 2 decimal places

7. Atomic Number Atomic number of an element is the number of protons in the nucleus of each atom of that element. Also equals the number of electrons. Element# of electrons # of protons Atomic # Carbon666 Phosphorus15 Gold79

8. B. Isotopes Atoms of the same element with different mass numbers. Same number of protons, different number of neutrons. Mass # Atomic # Nuclear symbol: Hyphen notation: carbon-12

9. Counting the Pieces Atomic Number = number of protons # of protons determines kind of atom Atomic Number = number of electrons in a neutral atom Mass Number = the number of protons + neutrons California WEB 12 6 C 14 6 C 12 6 C Mass Number = A Atomic Number = Z

10. Symbols Contain the symbol of the element, the mass number and the atomic number X Mass number Atomic number # protons and electrons in a neutral atom # protons + # neutrons Mass Number (Rounded to nearest whole number)

11. Symbols Find the –number of protons –number of neutrons –number of electrons –Atomic number –Mass number F 19 9 = 9 = 10 = 9 = 19 +

12. Symbols Find the –number of protons –number of neutrons –number of electrons –Atomic number –Mass number Br 80 35 = 35 = 45 = 35 = 80 http://www.chem.purdue.edu/gchelp/liquids/bromine.gif

13. Symbols Find the –number of protons –number of neutrons –number of electrons –Atomic number –Mass number Na 23 11 Sodium atom = 11 = 12 = 11 = 23

14. Symbols If an element has an atomic number of 23 and a mass number of 51 what is the –number of protons –number of neutrons –number of electrons –Complete symbol V 51 23 = 23 = 28 = 23

15. Symbols If an element has 60 protons and 84 neutrons what is the –Atomic number –Mass number –number of electrons –Complete symbol Nd 144 60 = 60 = 144 = 60

16. Symbols If a neutral atom of an element has 78 electrons and 117 neutrons what is the –Atomic number –Mass number –number of protons –Complete symbol Pt 195 78 = 78 = 195 = 78

17. 3545358035Br 1822184018Ar 20 4020Ca e–e– n0n0 p+p+ Mass # Atomic # Ca 40.08 20 Ar 39.948 18 Br 79.904 35