1. Chapter 6 State Standards: 3.a; 7.b 1Contreras

2. The Atom 2Contreras

3.  There have been many changes that have contributed to what the atomic theory is today  Over centuries many scientist have discovered and clarified information about the atom 3Contreras

4.  The atom is the smallest particle within an element  An element is made-up of MANY atoms that are exactly the same  Atoms cannot be seen with the naked eye 4 It would take 106 million billion Au atoms to cover the surface of a dollar bill 70 million He atoms could fit on your pencil eraser Contreras

5.  Nucleus – small, dense, positively charged center  Protons – positively charged particles in the nucleus  Neutrons – particles in the nucleus with no charge  Electrons – negatively charged particles found in electron clouds outside the nucleus. Determines size of atom. 5Contreras

6. 6 Electron Cloud Contreras

7.  Protons  1 amu  Positively charged (+)  Neutron  1 amu  No charge  The nucleus is the biggest part of the atom 1 amu = 0.0000000000000000000000017 g Atomic Mass Unit (amu ) 7 If there was a nucleus the size of a grape, it would have a mass of 9 million metric tons (18 million pounds)! Contreras

8.  Electrons  Negatively charged (-)  Found only in electron clouds  Smallest mass particle of the atom  1/1800 size of proton and neutron  Electron Cloud  Region outside the nucleus where electrons are contained 8Contreras

9. Atoms and Elements 9Contreras

10. 1. Gravitational Force – holds all the parts of the atom together 2. Electromagnetic Force – attracts electrons (-) around nucleus (+) 3. Strong Force – holds protons in nucleus together 4. Weak Force – holds nucleus together in radioactive atoms 10Contreras

11.  Nucleus has a positive charge (because of protons)  Electrons have negative charge  For an atom to have no charge, positive and negative charges need to be balanced (# of protons and electrons is equal)  An ion is an atom with a charge  Positively charged ion = atom has lost 1+ electron(s)  Negatively charged ion = atom has gained 1+ electron(s) 11Contreras

12.  Atomic number - # of protons in nucleus  Atomic number (# of protons) is the same for all atoms of a certain element  Atomic number tells you what element it is!  Atomic mass (mass number) = protons + neutrons  Atomic mass needs to be rounded 12 Atomic mass Contreras

13. Electron Cloud Maximum # of Electrons 12 28 318 432 13Contreras

14.  An element’s atomic number tells where it is on the periodic table Atomic number = # protons (+) # protons (+) = # electrons (-)  As long as the atom is not an ion Atomic mass = protons + neutrons 14Contreras

15. Isotopes 15Contreras

16.  Atoms of the same element that have different number of neutrons in their nucleus  Isotopes still have same:  Atomic number  # protons  # electrons  Different # neutrons  Named according to the mass number  hydrogen-1 and hydrogen-2 16Contreras

17.  Hydrogen has an atomic number of 1  So Hydrogen has 1 proton  Hydrogen has 2 additional isotopes (H with different number of neutrons)  Deuterium (1 proton & 1 neutron)  Tritium (1 proton & 2 neutrons) 17Contreras

18. 18  To find the number of neutrons:  Protons + neutrons = mass number  Mass number – atomic number (# proton) = neutrons  Mass numberof Carbon is 12 Mass number: 12 Atomic number: - 6 # Neutrons: ~6 Contreras

19.  An unstable atom where the nucleus will change and eventually fall apart over time  Will give off energy when they fall apart  Ex. Radon; Uranium  Found in nature  No stable isotope exists 19 http://computershopper.com/shoptalk/Radioact ive_Man_Number_One_v_1024.jpg Contreras

20.  Ions have a charge  Positive charge if lost an electron ▪ K 1+ has lost an electron  Negative charge if gained an electron ▪ Cl 2- has gained two electrons  Isotopes  Have same number of protons & electrons, different number of neutrons 20Contreras

21. NameLocationCharge NucleusCenter of atomPositive ProtonNucleusPositive NeutronNucleusNone ElectronElectron cloudNegative electron  proton/neutron  nucleus  atom  element smallest mass  biggest mass 21Contreras