Unit 1 - Atomic Structure PDF

Unit 1 - Atomic Structure Owner R Ryan Tags Notes Atomic Structure (Unit 1) UNIT 01.pdf Key Topics Covered: 1. Electricity: Direct Current (DC): Flows i...

Unit 1 - Atomic Structure Owner R Ryan Tags Notes Atomic Structure (Unit 1) UNIT 01.pdf Key Topics Covered: 1. Electricity: Direct Current (DC): Flows in one direction - unidirectional Alternating Current (AC): Reverses its direction of flow at regular intervals - bidirectional 2. Early History of Electricity: Greeks discovered electricity with amber ("elektron"). William Gilbert identified materials that could be charged rubbing silk on glass (+) or rubbing wool on rubber (-) repulsion → force that repels similarly charged matter attraction → force that attracts oppositely charged matter 3. Atoms: a. the basic building block of the universe b. all matter is made from a combination of atoms i. matter is any substance that has mass and occupies space ii. mass → quantitative measure of inertia or the resistance that a body of matter offers to a change in speed or position upon applying a force Unit 1 - Atomic Structure 1  1. the greater the mass of a body, the smaller the change produced by an applied force iii. element → a substance that cannot be chemically divided into two or more simpler substances Principal Parts: Proton: Positively charged. Electron: Negatively charged. Neutron: No charge. protons and neutrons combine to form the nucleus of the atom number of protons in the nucleus determine the element atomic number = # of protons NOTE: Hydrogen (H) does not contain a neutron Atomic number: Number of protons in an atom's nucleus. 4. The Law of Charges: opposite charges attract and like charges repel similarly charged objects repel each other because their lines of force can never cross each other Unit 1 - Atomic Structure 2  positive and positive proton both have outward lines of force and negative and negative charged objects both have inward lines of force because the nucleus has a net positive charge the electron is attracted to the nucleus gluon is a quark or force that holds the nucleus together 5. Bohr's Model of the Atom: Electrons orbit the nucleus in set paths, much like planets around the sun. electron orbit contains a set number of electrons number of electrons is found by using 2N^2 where N = number of the orbit or shell Unit 1 - Atomic Structure 3  valence electrons → electrons in the outer shell of the atom in the valance shell valence shell cannot contain more than 8 electrons noble gases contain 8 valence electrons (argon, krypton, xenon, and radon) protons = electrons so net charge = 0 and this is the stable condition of the atom atoms with 8 valence electrons are very stable these atoms are called noble gases and they are inert Inert means chemically inactive or unreactive. Noble gases are inert because their outer electron shell is full, making them extremely stable and unlikely to form chemical bonds with other elements. atoms with less than 8 valence electrons are less stable, and an external energy force can cause these valence electrons to escape the attraction of the nucleus atoms with 1-3 valence electrons are the least stable and can give up these valence electrons with less energy applied when an electron receives enough energy from some other source it quantum jumps into a higher allowed orbit and then returns to a lower orbit this causes the electron to emit excess energy as a single photon of electromagnetic energy and this movement of electrons by the external energy source is the basis of electric current flow 6. Electron Flow: Bump Theory: Electrons transfer energy by knocking into each other, causing current flow. like the energy a cue ball gives to a stationary ball some of the energy is released in the form of heat If a moving electron strikes an atom containing two valence electrons, the energy of the striking electron is divided between the two valence Unit 1 - Atomic Structure 4  electrons If the valence electrons are knocked out of orbit, they contain only half the energy of the striking electron when an electron receives enough energy from another source, it “quantum jumps” into a higher allowed orbit, but electrons tend to return to a lower allowed orbit as the electron emits excess energy as a single photon of electromagnetic energy photons are the smallest possible packets of electromagnetic energy this movement of electrons caused by the external energy source is the basis of the electric current flow electrical current is the flow of electrons 7. Conductors, Insulators, and Semiconductors: Conductors: 1-3 valence electrons (allow easy electron flow) = silver, copper, gold and aluminum materials that permit electrons to flow through them easily resistance increases with an increase in temperature Insulators: 7-8 valence electrons (resist electron flow) = rubber, plastic, glass, and wood materials that resist the flow of electricity 1. valence shell is almost full so it resists giving up electrons Semiconductors: 4 valence electrons resistance decreases when heated (e.g., silicon and germanium) neither good conductors nor insulators diodes, transistors, and integrated circuits 8. Power Sources a. theory that all electric power sources produce a positive terminal and negative terminal i. negative terminal = excess electrons forming at that terminal Unit 1 - Atomic Structure 5  ii. positive terminal = removing large number of electrons from that terminal iii. when a circuit is completed between the two terminals, negative electrons are repelled away from the negative terminal and attracted to the positive terminal 1. the greater difference in the number of electrons between - and + terminals, greater the force of repulsion and attraction 9. Molecules: Smallest unit of a compound (e.g., water). 10. Methods of Producing Electricity: magnetism (generators and alternators) chemical action (chemical ions in batteries) pressure (striking, bending, twisting crystals for piezo effect) heat (thermocouples) Unit 1 - Atomic Structure 6  friction (static electricity) light ( 11. Electrical Effects: Magnetism (anytime an electrical current flows through a conductor, a magnetic field is created around the conductor) chemical reactions (electroplating, electrolysis) pressure heat (electric ranges, irons, heaters) light Key Concepts & Definitions: 1. Atom: The smallest unit of matter, composed of protons, neutrons, and electrons. Example: A hydrogen atom contains one proton and one electron. 2. Electricity: The flow of electrons that generates power. Example: A light bulb turning on when connected to a power source. 3. Direct Current (DC): Electricity that flows in one direction. Example: Batteries produce direct current. 4. Alternating Current (AC): Electricity that changes direction periodically. Example: The electricity in homes is alternating current. 5. Conductors: Materials that allow electricity to flow easily because they have few valence electrons. Example: Copper wire is a good conductor. 6. Insulators: Materials that resist the flow of electricity because they have many valence electrons. Example: Rubber and glass are insulators. Unit 1 - Atomic Structure 7  7. Semiconductors: Materials with four valence electrons, neither good conductors nor insulators, whose conductivity increases when heated. Example: Silicon is used in computer chips. 8. Electron Flow: The movement of electrons from atom to atom, essential for the creation of electrical current. Example: In a circuit, electrons flow through wires from the power source to the device. 9. Valence Electrons: Electrons in the outermost shell of an atom, determining the atom's ability to conduct electricity. Example: A copper atom has one valence electron, making it a good conductor. 10. Photon: A particle of light or electromagnetic radiation, produced when electrons change energy levels. Example: Photons are emitted from a light bulb. The atom is the smallest part of an element. The three principal parts of an atom are the proton, the electron, and the neutron. Protons have a positive charge, electrons a negative charge, and neutrons no charge. Valence electrons are located in the outer orbit of an atom. Conductors are materials that provide an easy path for electron flow. Conductors are made from materials that contain from one to three valence electrons. Insulators are materials that do not provide an easy path for the flow of electrons. Insulators are generally made from materials containing seven or eight valence electrons. Semiconductors contain four valence electrons. Unit 1 - Atomic Structure 8  Semiconductors are used in the construction of all solid-state devices, such as diodes, transistors, and integrated circuits. A molecule is the smallest part of a compound. Six basic methods for producing electricity are magnetism, chemical action, light, heat, pressure, and friction. Five basic effects that can be caused by electricity are magnetism, chemical reactions, light, heat, and pressure. A photon is a massless particle of pure energy. Photons can be produced when electrons move from one energy level to another. Unit 1 Review Chapter 1 Review Questions 1. What are the three principal parts of an atom, and what charge does each carry? a. proton (+) b. neutron (no charge) c. electron (-) 2. How many times smaller is an electron than a proton? a. 3. How many times more does a proton weigh than an electron? 4. State the law of charges. a. like charges repel, opposite charges attract 5. How many valence electrons are generally contained in materials used for conductors? 6. How many valence electrons are generally contained in materials used for insulators? Unit 1 - Atomic Structure 9  7. What is electricity? 8. What is a gluon? a. a subatomic particle or quark that holds the nucleus together via an electromagnetic force (gravity called hold the nucleus together 9. It is theorized that protons and neutrons are actually formed from a combination of smaller parti- cles. What are these particles called? What is a coulomb? 2. What is an ampere? 3. Define voltage. 4. Define ohm. 5. Define watt. 6. An electric heating element has a resistance of 16 V and is connected to a voltage of 120 V. How much current will flow in this circuit? 7. How many watts of heat are being produced by the heating element in Question 6? 8. A 240-V circuit has a current flow of 20 A. How much resistance is connected in the circuit? 9. An electric motor has an apparent resistance of 15 V. If 8 A of current are flowing through the motor, what is the connected voltage? 10. A 240-V air-conditioning compressor has an apparent resistance of 8 V. How much current will flow in the circuit? 11. How much power is being used by the motor in Question 10? 12. A 5-kW electric heating unit is connected to a 240-V line. What is the current flow in the circuit? 13. If the voltage in Question 12 is reduced to 120 V, how much current would be needed to produce the same amount of power? 14. Is it less expensive to operate the electric heating unit in Question 12 on 240 V or 120 V? Unit 1 - Atomic Structure 10 Unit 1 - Atomic Structure 11