Chapters 4 and 25 – Atomic Theory and Nuclear Chemistry (Kahoot, PowerPoints) – Flashcards
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What type of radiation can be blocked by a sheet of paper?
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alpha
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this form of radiation has almost no mass and is similar to an electron:
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beta
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Which form of energy has the most energy?
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gamma
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Which type of nuclear reaction splits a larger atom into smaller atoms?
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fission
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Which type of nuclear reaction fuses two smaller nuclei to make a larger atom?
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fusion
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Why do nuclei undergo alpha and beta decay?
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to make the nucleus more stable to get a better ratio between protons and neutrons
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What is half life?
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the time for half of a substance to decay
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100 grams of a substance has a half life of 10 years. How much is left after 20 years?
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25 grams
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Which type of radiation would you have to swallow for it to seriously harm you?
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alpha
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Radiation was responsible for the powers of which superheroes?
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Spider-Man Hulk Superman
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Which scientist in 430 BC suggests that matter is made up of atoms - but can't prove it?
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Democritus
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Which scientist in 335 BC teaches that the world is made up of earth, fire, wind, and air?
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Aristotle
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This scientist in 1803 proved atoms exist - his atomic model was called "Billiard Ball" model.
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Dalton
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scientist in 1911 that discovered the positively charged nucleus with electrons around it
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Rutherford
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scientist who found electrons and is credited with the "Plum Pudding" model of the atom
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Thomson
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scientist who discovered that the number of electrons in the outer shell determine properties
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Bohr
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scientist in 1932 who discovered the neutron
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Chadwick
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scientist in 1922 proposed that electrons are both a particle and a wave - "duality"
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Schrodinger
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What two particles are inside of the nucleus and give the atom its mass?
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protons and neutrons
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What is the rule to follow when filling up electron shells for a Bohr model?
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2-8-8
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What are elements?
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pure substances with only one type of atom and can't be broken down by ordinary chemical means
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Who came up with the particle theory of matter in Greece, atomos meaning indivisible, but couldn't prove it because they only trusted their reasoning?
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DEMOCRITUS and Leucippus
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What did Aristotle contribute to the atomic theory?
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all substances are made of water (wet), fire (hot), earth (cool, heavy), and air (light)
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What is a chemical reaction?
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transformation of a substance(s) into one or more new substances
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Describe the revolution of the study of matter (emphasis on... interest in... what led to what)
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emphasis on quantitative analysis lots of interest in atmospheric gases better balances --> better masses for elements and compounds
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Who came up with the Law of Conservation of Mass, and what is it?
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Antoine Lavoisier mass is neither created nor destroyed in chemical or physical reactions mass of reactants = mass of products
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Who came up with the Law of Definite Proportions, and what is it?
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Joseph Proust like a chemical formula exact proportions of element-to-element chemical compounds have exact composition regardless of sample size or source of sample
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Who came up with the Law of Multiple Proportions, and what is it?
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John Dalton elements combine in a ratio of small whole numbers same two elements can have different proportions of mass for each compound
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What is Dalton's atomic theory?
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1. all matter is composed of tiny particles called an atom 2. atoms of a given element are identical in size, mass (not true because of isotopes), and other properties 3. atoms of different elements differ in mass and other properties 4. atoms cannot be subdivided, created, or destroyed (in ordinary chemical reactions) 5. atoms of one element can combine with atoms of another element to form compounds: new, complex particles
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How did Dalton sketch atoms?
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simple, indivisible small spheres
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Dalton turned ___________________'s ideas into scientific theory (tested), but what part of Dalton's theory is incorrect?
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Democritus Dalton said atoms are indivisible, BUT atoms are divisible into smaller particles in nuclear reactions
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What is the modern atomic theory?
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1. all matter is composed of atoms 2. atoms of any one element differ in properties from atoms of another element 3. atoms cannot be subdivided, created, or destroyed in ordinary chemical reactions, CAN occur in nuclear reactions 4. atoms of an element have a characteristic average mass which is unique to that element
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What is a compound?
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substance made by bonding atoms together in specific ways, contain two or more different types of atoms
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What is an atom?
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smallest particle of an element that retains the chemical properties of that element
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Who discovered electrons by using a cathode ray tube? Where did he think the electrons were located?
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JJ Thomson electrons like plums in a positive pudding
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What is JJ Thomson's atomic model called?
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Plum-Pudding model
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Describe Thomson's CRT (cathode ray tube) experiments.
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- particles pass through the tube from the cathode, the metal disk connected to the negative terminal of the voltage source, to the anode, the metal disk connected to the positive terminal - cathode ray tubes (CRT) pass electricity through a gas that is contained at a very low pressure (gases at normal atm pressure don't conduct well) - used different gases ; different metal electrodes - all results the same - luminous 'ray' could force paddle wheel to turn - so must be particles hitting it - initiated by electric current but must be interacting with something in gas - deflected by magnetic field, same as a wire carrying current - deflected away from (-) charge, towards (+) - 1897: successfully measured Cathode ray particle/mass - ALWAYS same CONCLUSION: - elements must contain identical negative electrons - atoms are neutral, so there must be positive particles in the atom to balance the negative electrons - electrons have so little mass that atoms must contain other particles that make up most of the mass
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What is the conclusion of the CRT experiments?
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- elements must contain identical negative electrons - atoms are neutral, so there must be positive particles in the atom to balance the negative electrons - electrons have so little mass that atoms must contain other particles that make up most of the mass
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Who determined the mass of the electron?
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Robert Milikan
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Describe Rutherford's Gold Foil Experiment. What did it discover?
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- extremely thin piece of gold foil was bombarded with fast-moving alpha particles - alpha particles: positively charged particles (basically a He nuclei) - looking for particles - particles hit the detecting screen (film) & are recorded - expected the alpha particles to pass trough with only slight deflection - beginning of photography and TVs - found: most alpha particles were observed to pass straight through gold foil - a few were scattered at large angles, some deflected back toward the source - Rutherford explained it was "as if you had fired a 15-inch (artillery) shell at a piece of tissue paper and it came back" discovered the nucleus: small, dense, and positively charged particle
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Who discovered the nucleus and how?
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Earnest Rutherford gold foil experiment
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What is the nucleus?
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small, dense, and positively charged particle
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state the symbol, charge, rounded mass, and location of - protons - neutrons - electrons
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protons: - p+ - positive - mass: 1 - nucleus neutrons: - n to the 0 - neutral - mass: 1 - nucleus electrons: - e- - negative - mass: 0 - electron cloud
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What is electrostatic repulsion?
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when like forces repel (example: +/+, -,-)
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What holds atoms together?
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strong and weak nuclear forces
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What are some attractive nuclear forces?
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neutron-neutron proton-neutron - strongly attracted when very close proton-proton - stay together in nucleus because nuclear force is greater than repulsion due to electrostatic force
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Where does the mass of the atom come from?
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nucleus: protons and neutrons
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What takes up the volume of the atom come from?
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empty space
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Nuclei have high/low densities?
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incredibly high densities only black holes are more dense
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Are protons and neutrons fundamental particles?
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no
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What are quarks?
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fundamental particles component of protons and neutrons
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Protons are made of what quarks?
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two up one down
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Neutrons are made of what quarks?
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one up two down
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How many quarks make up a proton or neutron?
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3
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What are quarks held together by?
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gluons
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What is the atomic number?
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Z number number of protons (smaller whole number)
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The periodic table is written in increasing...
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atomic number
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all atoms of an element have the same number of...
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protons
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What are isotopes?
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atoms of the same element that have different masses
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nuclide =
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isotope general term for a specific isotope of an element
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mass number:
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total number of protons and neutrons that make up the nucleus of an isotope (bigger decimal number) mass # = p+ + n0
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What is hyphen notation?
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name of element, hyphen, and mass number carbon-14
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What does a nuclear symbol look like?
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symbol of element with two numbers to the side top number = mass/A number bottom number = atomic/Z number
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What is an ion?
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atom with an electrical charge
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cation =
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+ion, more protons than electrons forms when an atom loses one or more e-
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Why do metals lose electrons?
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to attain noble gas configuration
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What are anions?
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-ion, more electrons than protons nonmetals gain electrons
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Where does the charge of an atom come from?
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protons and electrons
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What are forces in the nucleus?
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strong and weak nuclear forces: proton-proton proton-neutron neutron-neutron
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What's the difference between nuclear reactions and normal chemical reactions?
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- nuclear reactions involve the nucleus, chemical reactions don't - nucleus opens and protons and neutrons are rearranged, normal chemical reactions only involve electrons - binding energy holds nucleus together - strong nuclear forces
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What is binding energy?
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strong nuclear forces that holds nucleus together
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What did Marie Curie do?
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- discovered radioactivity (the spontaneous disintegration of some elements into smaller pieces) - found one of the pieces of evidence showing that atoms are made of smaller particles
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What is radioactivity?
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the spontaneous disintegration of some elements into smaller pieces
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What are radionuclides/radioisotopes?
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isotopes with unstable atomic nuclei that are radioactive
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What are the driving forces of atoms?
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lowest potential energy stability
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radioactivity
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radioactive isotopes undergo nuclear reactions, emitting high-energy particles and/or electromagnetic radiation (radioactive decay)
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particles of alpha radiation:
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alpha particles: helium-4 nuclei only very large nuclei
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What radiation consists of a stream of electrons?
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beta
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When are beta particles created?
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neutron decays to a proton
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decay =
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radiation
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What radiation consists of high energy photons and often accompanies the other types of radiation?
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gamma radiation accompanies alpha and beta speed of light
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synthetic isotopes emit...
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positrons
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What are positrons?
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mass of an electron, but has a positive charge (same thing as an electron, except its charge) symbol: 0 to the e
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Mass and energy can be interchanged with each other. Why?
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e = mc squared takes energy to create mass
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What is electron capture?
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electron with charge of -1, mass number 0 inner-orbital electron is captured by the nucleus of its own atom in man-made, synthetic elements
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What must balance in a nuclear equation?
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atomic numbers and mass numbers
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What do you use to fill in the missing protons and neutrons in balancing a nuclear equation?
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particle or isotope
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What radiation can be blocked by paper?
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alpha
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What radiation requires 0.5 cm of lead to be blocked?
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beta
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What radiation requires 10 cm of lead to be blocked?
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gamma
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What is mass defect?
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- small losses of mass in nuclear changes - difference between mass of atomic nucleus and mass of nucleons (protons and neutrons) can be converted into energy e = mc squared e = energy m = mass c squared = speed of light
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nucleons:
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protons and neutrons
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How come small amounts of mass are converted into enormous amounts of energy?
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because c squared is so large e = mc squared
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What is the Law of Conservation of Mass-Energy?
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sum of all energy and sum of all mass is a constant
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mass is conserved = _____________ is conserved
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energy
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higher binding energy =
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more stability in the nucleus
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transmutation:
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conversion of one isotope into another
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decay series/disintegration series:
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slide 32 radioactive nucleus reaching a stable state by a series of steps
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band of stability:
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known isotopes are plotted according to numbers of protons and neutrons, band forms - all stable nuclei in band - band includes some unstable isotopes because smooth lines can't be drawn without them above and below band: radioactive and unstable nuclear stability: 1:1: protons to neutrons
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decay will occur to ___________ to the band of stability
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return the nucleus
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half-life:
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period of time it takes for a given sample of a radionuclide/radioisotope to decay to half of its initial amount
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How far will a radioactive element decay to?
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to nothing good for nuclear medicine
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What are the types of nuclear reactions?
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fusion: combining two light nuclei to form a heavier, more stable nucleus (sun) fission: splitting a heavy nucleus into two nuclei with smaller mass numbers
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What is a chain reaction?
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self-sustaining fission process
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What is subcritical fission?
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; 1 neutron, reaction stops
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What is critical fission?
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1 neutron, sustained reaction
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What is supercritical fission?
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; 1 neutron, violent explosion
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What factors do not affect nuclear reactions, but do affect chemical reactions?
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Nuclear reactions are not affected by changes in temperature, pressure, or the presence of catalysts. Nuclear reactions of a given radioisotope cannot be slowed down, sped up, or stopped.
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mass number in periodic table
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most stable isotope
