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
Low-carbon economy wikipedia , lookup
Energy efficiency in transport wikipedia , lookup
Negawatt power wikipedia , lookup
Conservation of energy wikipedia , lookup
Energy policy of the European Union wikipedia , lookup
Energy Independence and Security Act of 2007 wikipedia , lookup
Photoelectric effect wikipedia , lookup
Basic Chemistry Atoms and Elements Matter • Matter: The material from which all substances are made • Matter 1. Has mass 2. Takes up space 3. Is composed of atoms Atoms • Atom - the smallest unit of matter • Atoms are composed of smaller subatomic particles – Proton: (+) charge – Electron: (-) charge – Neutron: no charge • Atoms are electrically neutral • Atoms have two major zones: – Atomic nucleus • Contains most of the energy and atomic mass • Contains protons and neutrons – Electron cloud • Determines reactivity Electron cloud He (Helium) Elements: Properties of Atoms • The properties of an atom are determined by the structure of an atom Number of protons, neutrons, and electrons • 1. Distance of the electron cloud from the nucleus 2. Arrangement of electrons in the cloud • Element: Matter composed of only one type of atom – • Ex. C and H are elements, but CH4 is not! Elements are arranged by structure (and therefore by properties) in the Periodic Table of Elements Periodic Table of Elements / http://www.ptable.com The other 2% of elements in organisms are called trace elements 98% of the mass of all living organisms is composed of the six yellow elements CHONP(S) Atomic Number • Atomic number: The number of protons in an atom • An element is defined by its atomic number – Ex. If an atom has 2 protons (atomic # 2) it is helium, 3 protons it is lithium, etc. • atomic # = # protons = # electrons; remember atoms are electrically neutral!! Atomic Mass • Atomic mass: the weight of an atom in Daltons (1 Dalton = 6.02 x 10-23 grams) – Recognize that number? • The atomic mass (in Daltons) of an element is roughly equal to the # of protons + # of neutrons in the atom – # neutrons = rounded atomic mass – atomic number • How many neutrons does a standard helium atom have? Determining the numbers of subatomic particles in a carbon atom using the Periodic Table of Elements: 1. Find carbon in the table: it has atomic number 6 and atomic mass 12.011 2. Atomic number 6 means that carbon has 6 protons and 6 electrons (atomic number = # protons = # electrons) 3. Round the mass number to the nearest whole number and subtract the # protons (or atomic number) to get # neutrons • • • # neutrons = rounded atomic mass – atomic number 12.011 ≈ 12; 12-6 = 6 neutrons Carbon has 6 protons, 6 electrons, and 6 neutrons • Determine the numbers of subatomic particles (protons, neutrons, and electrons) in the following atoms {use a periodic table}: – 6C – 8O – 17Cl – 7N – 3Li • Answers: – 6C – – – – = 6 protons, 6 neutrons, 6 electrons 8O = 8 protons, 8 neutrons, 8 electrons 17Cl = 17 protons, 18 neutrons, 17 electrons 7N = 7 protons, 7 neutrons, 7 electrons 3Li = 3 protons, 3 neutrons, 3 electrons Electrons and Periodicity • A row in the Periodic Table is called a period and corresponds to an energy level – The first period along the top contains the elements H and He – H and He contain only 1 energy level in their electron clouds • A column in the Periodic Table is called a group; members of a group have similar reactivity (Group 1) (Group 2) (Period 1) (Period 2) (Period 3) (Group 3) Electron Cloud: Energy Levels • The electron cloud is divided into electron shells or energy levels • An atom’s outer energy level is its valence shell and the electrons it contains are valence electrons – An atom has as many energy levels as the period (row) it is in {periodic table} – An atom has a number of valence electrons = to its Group (column) • Remember that some periodic tables count transition metals as groups; on these tables subtract 10 from the nonmetal group numbers to get the valence electron. Ex: group 14 = 4 valence electrons – Valence electrons determine reactivity • Determine the numbers of energy levels and valence electrons in the following atoms {use a periodic table}: – 6C – 8O – 15P – 7N – 1H • Answers: – 6C – – – – = 2 energy levels, 4 valence electrons 8O = 2 energy levels, 6 valence electrons 15P = 3 energy levels, 5 valence electrons 7N = 2 energy levels, 5 valence electrons 1H = 1 energy level, 1 valence electrons Alternative Elements: Isotopes • Isotope: an atom that has a number of neutrons different from the average for that element • Regular atoms usually more stable • Isotopes occur naturally; the average mass numbers of isotopes and normal atoms of one type is atomic weight mass ≈ 1.000 2H mass ≈ 2.012 3H mass ≈ 3.014 +______________ 6.026 Div by 3 ________________ Atomic Wt ≈ 1.008 1H Alternative Elements: Radioisotopes (Radionuclides) • Radioisotopes: Isotopes with unstable nuclei that may emit high energy particles – ‘Adding’ neutrons weakens the strong nuclear force and destabilizes the nucleus – The nucleus will regain stability by ejecting particles • Radiation: Energy particles emitted by a radioisotope Uses for Radioisotopes • Used in body scans • Used as radiotracers to determine steps of internal chemical processes – Radioisotopes were used to puzzle out the steps of photosynthesis, cellular respiration, and viral infection among others • Can be used date rocks, artifacts, and bones – Called radiometric dating • Used to treat cancer (chemotherapy) and other disorders • Massive or prolonged exposure causes damage to organisms Fiestaware Demo Electron Clouds • Divided into energy levels • Energy levels divided into orbitals Orbitals The Octet Rule • Lewis dot diagram: A diagram of a period 1, 2, or 3 element that shows the distribution of valence electrons in an atom • Octet rule: A period 2 or 3 element has a full valence shell when it has or can share 8 valence electrons • Lewis dot diagrams are used to determine whether and how two elements will covalently bond • Do a Lewis Dot Diagram of the following atoms: – 6C – 1H – 8O – 7N – 15P – 16S Basic Chemistry ELECTRON PHYSICS Physics - Background • In order to do work, all machines must transform energy from one form to another – Work is what is accomplished when a force operates on an object over a distance. – Energy is the capacity to do work, or the capacity to change. – Force is defined as a push, pull on an object • The transformation of energy is a requirement of life (part of metabolism) – Energy transformations are linked to chemical transformations in cells • Remember: Energy → Force → Work Physics- Potential Energy All forms of energy can be placed in two categories: …is realized • Potential energy is stored energy—as chemical bonds, concentration gradient, charge imbalance, etc. • Once energy is actually converted, it is no longer potential energy; it is real energy Potential energy…. Question: • Just as energy can be converted from potential to real, it can be converted from one type to another. There are many types of energy; can you name some? Physics - Thermodynamics There are two rules for the conversion of energy (the Laws of Energy): 1. Energy is neither created nor destroyed. The total amount of energy before a transfer equals the amount of energy after (in a closed system). 2. No conversion or transfer of energy is 100% efficient. The amount of energy useable for work after a conversion is less than before the conversion. The “lost energy” escapes as waste heat. This phenomenon is called entropy. Problem: • A hypothetical car converts the chemical energy in gas to kinetic energy (via the engine), and kinetic to electrical (via the alternator) to power the radio. If both the engine and the alternator are 20% efficient, and there is 100 calories of energy in the gas, how much is left to power the radio after conversion? How much energy is lost? Answer: • A hypothetical car converts the chemical energy in gas to kinetic energy (via the engine), and kinetic to electrical (via the alternator) to power the radio. If both the engine and the alternator are 20% efficient, and there is 100 calories of energy in the gas, how much is left to power the radio after conversion? How much energy is lost? – 100 cal (chemical) to 100 cal (.20) kinetic to 100 cal (.20)(.20) electrical. 100 cal → 20 cal → 4 cal – 4 calories are left for the radio. 96 calories were wasted. Problem: • An mechanic with little grasp of Thermodynamics proposes an electrical car that uses an alternator claiming that the alternator will charge the car battery and keep the car going forever. What is wrong with his plan? Answer: • An mechanic with little grasp of Thermodynamics proposes an electrical car that uses an alternator claiming that the alternator will charge the car battery and keep the car going forever. What is wrong with his plan? – The alternator will actually drain all the power in the engine! For example: Imagine that the battery, which powers the car, has 100 cal of energy with a 20% efficient energy conversion rate. When the electrical energy is converted to kinetic energy, 20 cal will be usable Atomic Electrodynamics • Electrons have potential energy proportional to their distance from their nucleus – Farther = longer distance to fall = more potential energy! • Electrons in their original state are said to be in a ground state, but we can add energy to make them jump to a higher energy level; an excited state. – The jump lasts microseconds before the electron is snatched up by a nearby atom or falls back to the ground state. • Jumping electrons may go from a high energy state to a low or vice versa • The difference in energy is released or stored – Any stored energy can then be used to build ATP – Released energy emerges as heat or fluorescence (light emissions) • Some electrons may jump completely away from their atoms! The atoms are not ionized Basic Chemistry MOLECULES, REACTIONS & BONDING Elements vs. Molecules • Elements are composed of only one kind of atom (Ex O2) – Six elements make up 98% of organic molecule mass – Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur CHONP(S) • Molecules are composed of multiple kinds of atoms chemically bound together (Ex H2O) • Bonding occurs as a result of a chemical reaction, an interaction of atoms in which molecules change partner atoms to form new compounds* Covalent Bonds • Covalent bonds: Bond in which atoms share one or more pairs of electrons, so that the valence shells are filled • May bond double or triple The Octet Rule • Lewis dot diagram: A diagram of a period 1, 2, or 3 element that shows the distribution of valence electrons in an atom • Octet rule: A period 2 or 3 element has a full valence shell when it has or can share 8 valence electrons • Lewis dot diagrams are used to determine whether and how two elements will covalently bond Determine a possible structural formula of hydrogen and carbon 1. Find the elements on the Periodic Table and determine the number of valence electrons each has • Carbon is #4 (Group 4, so 4 valence) and hydrogen is #1 (Group 1 so 1 valence) 2. Do a Lewis dot diagram of each element 3. Determine where valence electrons can pair up • Do a Lewis Dot Diagram of the following atoms: – 6C – 1H – 8O – 7N – 15P – 16S Covalent bonds can be • Single—sharing one pair of electrons C H • Double—sharing two pairs of electrons C C • Triple—sharing three pairs of N N electrons Polar Covalent Bonds - Water • Polar covalent bonds – – – – Generate a polar (magnetic) molecule H2O is the classic example Molecules become magnetically ‘bent’ Causes the formation of a magnetic field with a (+) and a (–) end Unpaired electrons & shape Water is polar: it possesses two magnetic dipoles. Here the molecules are attracted to a statically charged balloon. Hydrogen Bonds