Chapter 2 Topics: Elements and the Periodic Table http://www.youtube.com/watch?v=1PSzSTilu_s Can you find the halogens? Alkali metals? Noble gases? Transition metals? Alkaline earth metals? Lanthanides and actinides? Metals? Nonmetals? Semimetals or metalloids? http://ed.ted.com/periodic-videos *Balancing Equations What coefficients balance this equation: Mg + Al2S3 → Al + MgS *Types of Reactions Classify the reaction type above. *These two topics will be on the 2b Exam, not the 2a Exam! Subatomic Particles! Particle Charge Mass Location Electron -1 1/1800 Outside the nucleus Proton +1 1 Inside the nucleus Neutron 0 1 + 1/1800 Inside the nucleus Atomic number is the number of protons. This tells WHAT element it is! The number on the Periodic table is the ATOMIC WEIGHT. This is an average mass of all the ISOTOPES that occur in nature. Atomic mass or mass number is a WHOLE number that must be rounded from the number on the periodic table. It is the number of protons + the number of neutrons in an atom of the element. Isotopes are atoms of the same element that have different MASSES. They have the same number of PROTONS, but different numbers of NEUTRONS. Isotope Notation! Isotopes of an element have the same physical and chemical properties. They only have different MASSES! 40 20Ca How many protons? What is the atomic number? What is the mass number? How many neutrons? How many electrons? (Hint: All atoms must be neutral!) 20 protons, atomic number 20, mass number 40, 20 neutrons, 20 electrons 21Ne How many protons? How many neutrons? How many electrons? 10 protons, 11 neutrons, 10 electrons 19 9X How many protons? How many neutrons? protons, 10 neutrons, What element is this? 9Fluorine An isotope of an element has 3 protons and 4 neutrons. Write its isotope notation. 73Li ATOMIC WEIGHT Lithium exists as two isotopes: lithium-7 and lithium-6 Lithium-7 has a mass of 7.015 amu and makes up 92.58% of lithium Lithium-6 has a mass of 6.015 amu and makes up 7.42% What is the atomic weight of lithium (on the periodic table)? Which isotope is more abundant, lithium-6 or lithium-7? To calculate the average atomic mass of lithium, multiply the mass of each isotope by its abundance, then add these 2 values to each other Mass Defect There's actually one more reason why the mass isn't a whole number.... recall that the mass of a neutron isn't exactly 1 amu. And when protons and neutrons stick together to make a nucleus, a small amount of mass is converted to energy, making a very strong bond called strong nuclear force. E=mc2 When an atom loses electrons it becomes a positively charged ion called a cation. IONS* Atoms are neutral because they have the same number of protons and electrons. *Ions will be on the 2b Exam *I* When an atom gains electrons it becomes a negatively charged ion called an anion. 39K+ How many protons does this isotope have? How many neutrons? How many electrons does this ion have? 19 protons, 20 neutrons, 18 electrons 16O2- How many protons does this isotope have? How many neutrons? How many electrons does this ion have? 8 protons, 8 neutrons, 10 electrons