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Chapter 11 section 2 questions the atom AutoSave September 21, 2012 1 Chapter 11 section 2 questions the atom September 21, 2012 Describe the size of an atom. A penny contains 20,000,000,000,000,000,000,000 atoms of copper and zinc. Aluminum atoms have a diameter of 0.00000003 cm (3 one hundred millionths). AutoSave 2 Chapter 11 section 2 questions the atom September 21, 2012 Name the parts of an atom. proton AutoSave neutron electron 3 Chapter 11 section 2 questions the atom September 21, 2012 Describe the relationship between numbers of protons, neutrons, and atomic number. Protons and neutrons are found in the nucleus and make up 99% of the mass of an atom (measured in AMU - atomic mass units). If you add protons and neutrons together they EQUAL the atomic mass. The number of Protons will ALWAYS remain the SAME for an element. If the number of protons changes - the element changes. The number of protons is ALWAYS EQUAL to the ATOMIC NUMBER!! To find the number of neutrons an atom is SUPPOSED to have, simply take the difference between the atomic number and the atomic mass (rounded to the nearest whole number). Sometimes the number of neutrons is different, thereby the element will have a different atomic mass. When this happens (the number of neutrons is not what it's supposed to be) we call it an ISOTOPE!! AutoSave 4 Chapter 11 section 2 questions the atom September 21, 2012 State how Isotopes differ. Isotopes have different atomic masses than what can be calculated normally. For Example: Helium has an atomic number of 2 and an atomic mass of 4. Therefore, it has 2 protons and 2 neutrons. If Helium has 4 neutrons instead, it is an ISOTOPE. We would write this Isotope as He-6. The 6 tells you the atomic mass of the element listed!! AutoSave 5 Chapter 11 section 2 questions the atom September 21, 2012 Describe the forces within an atom. Gravitational - amount of force between 2 objects Electromagnetic - Opposites attract (positive/negative) Strong Force - in the nucleus Weak Force - radioactive/unstable atoms AutoSave 6 Chapter 11 section 2 questions the atom September 21, 2012 Name the 2 kinds of particles that can be found in the nucleus. Protons and Neutrons What charge does the nucleus carry? ALWAYS POSITIVE!! AutoSave 7 Chapter 11 section 2 questions the atom September 21, 2012 How does an atom become a positively charged ion? Electrons are the negatively charged particles found in the energy levels that surround the nucleus - this like the rings on a target! Electrons have a VERY small mass - almost inconsequential to the atomic mass. Electrons carry a negative charge and are held in place by the positively charged protons. (BTW...Neutrons are NEUTRAL!) In a neutral atom - the number of protons is EQUAL to the number of electrons. Therefore they cancel each other out. Sometimes, during the chemical bonding process atoms can gain or lose electrons in the formation of new chemical bonds. When this happens an ION is formed. SO, if you have a POSITIVE ION - you have more protons than electrons (you lost electrons during the bonding process). If you have a NEGATIVE ION - you have more electrons that protons (you gained electrons during the bonding process). More on this as we progress:) AutoSave 8 Chapter 11 section 2 questions the atom September 21, 2012 In what cases are different isotopes important? They still have the same basic properties as the original atom. However, sometimes isotopes can be radioactive (or unstable). Meaning that they can change spontaneously. These radioactive isotopes are known for being used mostly in a lab setting. For example: Carbon-14 is used in radioactive dating materials that are believed to be no more than 50,000 years old. Ummmmm.... AutoSave 9 Chapter 11 section 2 questions the atom September 21, 2012 Draw and Label a model of a Helium (neutral) atom. Proton Electron Neutrons AutoSave 10 Chapter 11 section 2 questions the atom September 21, 2012 Draw and label a model of 2 different Hydrogen isotopes. Hydrogen Atom Neutral! Hydrogen Atom Neutral!! Hydrogen1 Hydrogen2 AutoSave 11 Chapter 11 section 2 questions the atom September 21, 2012 Math Focus...Calculating Atomic Mass 1. (.2 X 10 amu) + (.8 X 11 amu) = 10.8 amu 2. (.72 X 85 amu) + (.28 X 87 amu) = 85.56 amu 3. (.6 X 69 amu) + (.4 X 71 amu) = 69.8 amu 4. (.52 X 107 amu) + (.48 X 109 amu) = 107.96 amu 5. (.92 X 28 amu) + (.05 X 29 amu) + (.03 X 30 amu) = 28.11 amu AutoSave 12