Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
2/3/2016 Today Reminders: ◦ What are atoms made of? ◦ Problem Set 1 DUE online next Monday at 11 pm Protons Neutrons Electrons Sizes, Masses, Volumes ◦ Scientific Notation Using exponents to express large and small numbers Converting between standard notation & scientific notation Orders of Magnitude: Scientific Notation A tool for expressing incredibly large or incredibly small numbers WITHOUT using lots of zeros. ◦ Scientific notation is the combination of a exponential of 10 (10x). and an Example: There are approximately 400,000,000,000 stars in our galaxy. x 1011 1011 = 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 = 100,000,000,000 In proper scientific notation: The decimal part of the number is always expressed somewhere between 1 n < 10. 1 2/3/2016 Scientific Notation A positive exponent (n) means 1 multiplied by 10 n times. 104 = 10 ∙ 10 ∙ 10 ∙ 10 = 10,000 To change a number that is 10 or greater to scientific notation: count how many times you must move the decimal to the left to change the number to something between 1 and less than 10. ◦ The number you counted is the number of factors of 10 you are dividing out of the number and will be the exponent on the 10 in scientific notation. Scientific Notation A negative exponent (-n) means 1 divided by 10 n times. 10−4 = 1 1 1 = = = 0.0001 104 10 ∙ 10 ∙ 10 ∙ 10 10,000 To change a number less than 1 to scientific notation: count how many times you must move the decimal to the RIGHT to change the number to something between 1 and less than 10. ◦ That number is the number of factors of 10 you are multiplying into the number and the negative of that number will be the exponent on the 10 in scientific notation. Scientific Notation Expressing extremely small and extremely large numbers ◦ Atoms are very small. For example, 18 mL (~ 4 teaspoons) of water contains 602,200,000,000,000,000,000,000 molecules of H2O. A single water molecule has a mass of 2.99 x 10-26 grams. 2 2/3/2016 Theories of Matter Composition Democritus (5th – 4th century BC) ATOMISM Aristotle (4th – 5th century BC) CONTINUOUS MATTER FOUR ELEMENTS – Earth, Air, Fire, Water Boyle (17th century) Reintroduced ATOMISM in modern times. Dalton (19th century) Atomic Theory to explain results of EXPERIMENTS. The Discovery of the Electron The Discovery of the Nucleus 3 2/3/2016 The Discovery of the Nucleus Expected Result: Actual Result: How small are Atoms? A pebble is to Mt. Everest… …As an atom is to a pebble. It would take nearly ONE MILLION CARBON ATOMS, one after another, to add up to the width of a human hair Size of the Atom Vs. Size of the Nucleus If a single ATOM were the size of a football field… NUCLEUS (center of atom) In an atom: The majority of the space is taken up by electrons ELECTRON CLOUD The NUCLEUS would be the approximate size of a FLEA on the 50 yard line 4 2/3/2016 Elementary Particles & the Standard Model of Physics Mass Comparisons (Neutral) The electron is about 1800 times LESS massive than the proton (or neutron). Electrons orbit the nucleus in orbital clouds; the degree to which they spread out determines the overall size of the atom. The nucleus is composed of: PROTONS NEUTRONS Volume Comparison Mass Comparison If the atom were the size of a football field, the nucleus would be the size of a flea on the 50 yard line If the nucleus was as heavy as a bowling ball, the electrons would be as light as a penny. The space occupied by the electrons determines the size of the atom 5 2/3/2016 Rutherford’s model of the atom: An atom is made up of a incredibly small, central, positively charged nucleus, surrounded by even smaller, negatively charged electrons that are moving around the atom. NUCLEUS: 1) Subatomic particle: Core of the atom. 2) POSITIVELY CHARGED. 3) Takes up very little space in the atom. 4) Contains MAJORITY of the mass of the atom. (Figure is not to scale.) Charged Particles: The electrical charges on atoms DRASTICALLY influences the way they behave o The balance between positive charges (protons) & negative charges (electrons) determines the on an atom. What makes one Element different from another Element? ELECTRICAL CHARGES RULE CHEMISTRY • The identity of an element is determined by the number of protons in the nucleus. For example: any atom with 6 protons in the nucleus is a Carbon atom. • The number of protons in the nucleus = atomic number (Z) • Elements are arranged in the periodic table by their atomic number (Z) 6 2/3/2016 A Diversity of Elements: Differences originating in the nucleus from varying numbers of protons Elements are arranged in the periodic table by their atomic number (Z) Counting numbers of Protons & Electrons How many protons and electrons are in a Nitrogen (N) ANION that has a -3 charge overall? A. 7 protons & 7 electrons B. 4 protons & 7 electrons C. 7 protons & 4 electrons D. 7 protons & 10 electrons E. No enough information available to say 7