Chemistry Summative Test PDF

Atomic theory- 1. Who is the father of Atomic theory? - John Dalton 2. The term atomos, spoken by Democritus means - indivisible - Atoms cannot be created nor destroyed - Atoms are the most basic unit of matter - During a chemical change atoms cannot be created, destroyed or disappear, but...

Atomic theory- 1. Who is the father of Atomic theory? - John Dalton 2. The term atomos, spoken by Democritus means - indivisible - Atoms cannot be created nor destroyed - Atoms are the most basic unit of matter - During a chemical change atoms cannot be created, destroyed or disappear, but atoms do break apart. - Law of conservation of mass: no detectable change in mass in a chemical reaction - Law of definite proportions: compounds contain to same proportions of elements by mass - Ratio of atoms in a H20 molecule is: 1:2 3. J.J Thomson discovered…? - Electrons (negatively charged)’ - What evidence proves this? : cathode rays (which are made up of electrons), when holding the positive side of the magnet to the rays it went towards the magnet, but when holding the negative side to the rays it repelled from the magnet, therefore justifying opposites attract. 4. What is the charge of an alpha particle?: Positive 5. What happened to the alpha particles in the gold foil experiment: Most of the alpha particles went through the foil, but very few bounced/came back as if they had hit something. 6. How did Rutherford know the nucleus was positively charged?: Because when the positively charged alpha particles came in contact with the nucleus they repelled back. 7. How does the size of the nucleus compare with the size of the entire atom: The nucleus is very tiny, therefore why only few particles didn’t go through the particle. 8. Where is almost all the mass of the atom located?: the nucleus Abundance: - Boron-10 has an abundance of 19.9%, and the isotopes mass is 10.013 u. Boron-11 has an abundance of 80.1%, and the isotopes mass is 11.009 u. Calculate to verify the average atomic mass is 10.81 u. - Process: 10.013(.199) + 11.009(.801) = 10.811 amu Nuclear (ionizing) radiation: Band of Stability: 1. If an element had 90 protons, how many neutrons would be a good number for it to have in order to be a stable element? What element would this be? - Thorium, a good number of neutrons for it to be a stable element would be 142  2. Would a large atom (more than 40 protons) be found in nature if it has the same number of protons & neutrons (1:1 ratio)? - Less likely to exist naturally for atoms with more than 40 protons. The number of neutrons is not the same as the number of protons, no 1:1 ratio, therefore unstable. 3. Would a small atom (less than 20 protons) be found in nature if it has the same number of protons & neutrons (1:1 ratio)? Explain. - They would be found in nature, yes. They are in a 1:1 ratio concluding they are stable, resulting in them being found in nature. 4. How can there be two different atoms of carbon? How are they different? - They are different because of the number in their nuclei, since they differ, it leads to the element having different atomic masses. Vocabulary: 1. A positively charged particle made up of two protons and two neutrons and released by a radioactive nucleus is the _alpha particle_________. 2. An electron released by a radioactive nucleus that causes a neutron to change into a proton is called a _beta particle_________. 3. A nucleus that is unstable and will change over time is called a __radioactive________isotope. 4. The amount of time for half the atoms in a radioactive sample to decay is called the ___half-life_______. 5. The process in which the nuclei of unstable atoms can become more stable by emitting particles and/or electromagnetic radiation is called _radioactive decay_______________. 6. High-energy electromagnetic radiation released by a radioactive nucleus are called ___gamma rays_______. 7. ___Alpha_______ decay is the breaking up of a radioactive element, more often than not resulting in the formation of a new nucleus. 8. ___Transmutation______________ is the changing of an atom into another kind of atom that takes place during radioactive decay. _Marie Curie_________ discovered radioactivity, __she______________wins two Nobel Prizes for coining the term, and for discovery of the element __Polonium and Radium____________________. 9. Alpha radiation is actually a stream of (positively, negatively) charged particles. 10. Beta radiation is actually a stream of (positively, negatively) charged particles. 11. Whenever an element undergoes (alpha, beta, gamma) decay, it turns into another element with an atomic number two less than before and a mass number four less than before.  12. During (alpha, beta, gamma) decay, a neutron in the nucleus decays into a proton and an electron. 13. The more stable a nucleus is, the (longer, shorter) its half-life. 14. (Alpha particles, Beta particles, Gamma rays) can be stopped with a piece of paper. 15. (Alpha particles, Beta particles, Gamma rays) can be stopped with a thin metal sheet. 16. It takes a dense metal sheet, like lead, (or concrete) to stop (alpha particles, beta particles, gamma rays). 17. (Alpha particles, Beta particles, Gamma rays) travel at the speed of light. 18. The term radioactivity was coined by ___Marie Curie_______. 19. (Alpha particles, Beta particles, Gamma rays) are not affected by a magnetic field because they carry no charge. 20. An alpha particle is actually a nucleus of _a helium atom_________. 21. Beta particles originate in the __nucleus________ of the atom. 22. Radioactive decay processes occur until a ___stable_______ element is formed. 23. The half-life of a given isotope can be altered by heat, pressure, or some other physical means. True or False. 24. What happens in a chain reaction? a free neutron interacts with the nucleus of an atom and causes that nucleus to split apart into two new, less massive nuclei. 25. The type of nuclear reaction occurring within the sun and stars where nucleosynthesis happens is called ____. 26. Why is ionizing radiation more dangerous to children than to adults? Radiation is more dangerous to children because their bodies are still growing. 27. Branch of medicine where radioisotopes are used to diagnose and treat diseases is called_nuclear medicine__________. 28. A type of nuclear reaction where a nucleus splits into two daughter nuclei is called__fission________. 29. Synthetic elements, formed by bombardment reactions, are called __transuranium elements______________. 30. The last naturally occurring element is ___uranium______________. 31. The last element with any stable nuclei is __lead______________. - What kind of decay makes you able to lose a neutron? Beta decay - Radioisotopes are used to treat and diagnose diseases. - Tracer- a radioisotope introduced into a person’s body, its movement is traced - Parts of a nuclear reactor: Fuel, moderator, control rods History of the atom: 1. What are elements made of? - Elements are composed of atoms. 2. What are compounds made of?  - Atoms of different elements. (in whole number ratios) 3. What did Lord Ernest Rutherford discover: discovered alpha particles (positively charged) Chapter 2.1 - 2.2: Proton: mass nearly equal to a hydrogen atom, positive charge Neutron: an uncharged particle, mass slightly greater than a proton Atomic #: number is a basic property of an element - symbol is Z Mass #: = number of protons + number of neutrons To calculate the number of neutrons: mass # - protons - Same number of protons, different amount of neutrons is an isotope Chapter 2: Ex. Fe-56 is more abundant than Fe-54 because the atomic mass of iron is 55.8, which is closer to 56 than 54. Isobars: (different atomic number (Ca, Ar, K), same mass number, 41) Ca-41, Ar-41, K-41 Isotopes: (same atomic number, different mass numbers) Ca-40 Chapter 19: Radioactivity: Mode of decay: (naturally occurring radioactive nuclei decompose by) Alpha Particle Emission: in which an ordinary helium nucleus, is given off - When alpha emission occurs the atomic number decreases by 2 and the mass number decreases by 4. Beta Particle Emission: - Produces an electron - Given the symbol 0/-1 e - Beta emissions convert a neutron to a proton - Mass number stays the same, atomic number increases by 1 - Occurs with nuclei that contain “to many neutrons” for stability Gamma radiation emission: - Consists of high-energy protons - Gamma radiation changes neither the mass # or the atomic # - Normally omitted in writing nuclear equations Positron emission: a positron is identical to an electron except that it has a charge of +1 rather than -1 - Positron has the symbol 0/1 e - Ex. 40/19 K -----> 0/1 e +40/18 Ar - A proton of K-40 is converted to a neutron in Ar-40 - Positron emission is characteristic of nuclei that have to many protons for stability K-electron capture: - An electron in the innermost energy level “falls into the nucleus” - Ex. 82/37 Rb +0/-1 e ----> 82/36 Kr - Result of electron capture is the same as positron emission; mass number in unchanged, whereas atomic number decreases by 1 unit Nuclear Bombardment: - Effective for the lower numbers of the series (elements 93-95), but the yield of product decreases sharply with increasing atomic number - Ex. 27/31 Al + 4/2 He ----> 30/15 P + 0/1 n (2 things are being added to each other on each side is a good determination for nuclear bombardment) Nuclear medicine: - Radioactive isotopes are commonly used in cancer therapy - The medical speciality of using radioactive substances to diagnose and treat diseases Chernobyl disaster: -