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Name ____________________________P.__ Date___________ Atomic Structure and Theory Test Review (TEST IS ON ___________) Atomic Theory History 1) democritus is credited with naming the atom, which he said is the building block of all matter & means indivisible 2) Dalton believed the atoms were solid balls and that atoms of one element are different from the atoms of another element, but he didn’t know how they were different. 3) Using a cathode ray tube, Thomson identified the electron as a negative particle. He knew electrons were in atoms, so he came up with the plum pudding model. He thought the negative electrons were floating throughout a positive substance. Answer Bank for fill in atom anat. 0 amu 1 amu 14 15 16 17 18 21 21 22 24 27 Atomic number Average Decimal Different Identity Isotope Isotopes Mass Mass number Mass numbers Negative Neutral Positive Strong nuclear Sulfur Answer Bank for fill in atomic theory Solid Small Rutherford Positive Positive Plum pudding Planetary Nucleus Mass Indivisible Empty Electrons Electron cloud model Electron Different Democritus Cathode 4) Through his gold foil experiment, rutherford identified that the nucleus of an atom is positiveand that the atom is mostly empty space. Although the nucleus is just a small part of the atom, he found that the mass of the atom is in the nucleus. He came up with the planetary model, but he didn’t know that protons and neutrons were in the nucleus. 5) Bohr believed the electrons orbited the nucleus and that the nucleus contained neutrons and protons. The negative electrons are attracted to the positively charged nucleus. 6) The current model is the electron cloud in which the protons and neutrons are in the nucleus and the electrons are found in cloud-like regions surrounding the nucleus. Atom Anatomy 7) The nucleus of the atom holds the protons and neutrons. The nucleus is held together by the strong 1 nuclear force. Electrons are attracted to the positive nucleus and are found orbiting the nucleus. 8) Protons have a positive charge and a mass of 1 amu Neutrons have a neutral charge and a mass of 1 amu. Electrons have a negative charge and a mass of0 amu 9) The number of protons is the atom’s number . The number of protons also gives the atom itsidentity Change the number of protons, you will get a different type of atom. 10) The element sulfur has an atomic number of 16, so it has 16 protons. 11) The mass number of an atom is equal to its number of protons and neutrons, since both of these particles have a mass of 1 amu. If you alter the number of neutrons an atom has, you will alter its mass number. 12) An isotope is an atom of the same element but has a different mass number because it has more or less neutrons. 13) Scandium- 45 and Scandium- 48 are isotopes The 45 and 48 represent the mass #s of the two isotopes. Scandium-45 has 21 protons and 24 neutrons, whereas Scandium-48 has 21 protons and 27 neutrons. 14) Argon’s atomic number is 18 and its mass number is 40. Argon has 18 protons and 22 neutrons. 15) The atomic mass is different from the mass number because the atomic mass is an average of the masses of many atoms of the same element. This is why the atomic mass is a decimal but mass number is always a whole number. 16) Atom A, B and C are all atoms of the same element X. Atom A has 7 protons and 7 neutrons. Atom B has 7 protons and 8 neutrons. Atom C has 7 protons and 10 neutrons. a) The mass number for atom A is 14 b) The mass number for atom B is 15 c) The mass number for Atom C is 17 2 d) The average atomic mass for element X is 15.3 amu. (not in answer bank) e) 119 Sn - The atomic number of Sn is 50 and the mass number is 50 119 Sn has 50 protons and 69 neutrons. (not in answer bank) 17) Write a symbol which represents an isotope of Sn that has 67 neutrons. 11750Sn (not in answer bank) Ions 18) Atoms have the same number of protons and electrons which makes them electrically neutral 19) But, since electrons are found outside the nucleus, it is easy for an atom to lose or gain electrons, and when this happens, an atom becomes an ion 20) So if an atom of Flourine gains an electron it will become an ion of Flourine. It is still fluorine but it now has a negative charge. Answer Bank for fill in nuclear Many Unstable Radioactive Particles Alpha Weakest Gamma Helium Electron Energy Neutrons Neutrons Leaves One No effect Fission Fusion Chemical Half 1 1.5 2 4 84 Answer Bank for fill in ions Positively Never Neutral Lose Ion Gain Flourine Electrons Electrons 21) Atoms that gain electrons become negatively charged and atoms the lose electrons become positively charged. 22) An atom with a -3 charge gained 3 electrons and atom with a +2 charge lost 2electrons 23) Remember, atoms become ions by losing or gaining electrons. The number of protons is never altered to make ions. Nuclear Chemistry 24) Smaller atoms have stable nuclei when their neutron to proton ratio is 1:1. 25) Medium sized atoms have stable nuclei when their neutron to proton ratio is1.5: 1. 3 26) Atoms of atomic number 84 or more all have unstable nuclei because they just have too many protons and neutrons. 27) Atoms with too many or too few neutrons will also have unstable nuclei. These atoms are called radioactive 28) Unstable nuclei will lose energy and particles in order to make their nuclei stable. 29) Using the Band of Stability graph, is 119 Sn stable or unstable? Stable 50 (not in answer bank) 30) 3 types of particles are released by radioactive nuclei – alpha, beta, and gamma. 31) Alpha radiation is the weakest and can be blocked by paper. Gamma radiation is the strongest and can penetrate body tissues. 32) An alpha particle is the nucleus of a helium atom. The beta particle is a high energy electron The gamma particle is a packet of energy called a photon. 33) When an atom loses an alpha particle, it loses 2 protons and 2neutrons The atom’s atomic number decreases by 2 and its mass number decreases by 4 34) When atom goes through beta decay, one of its neutrons breaks down into a proton and an electron. The electron leave the nucleus, but the proton stays behind. This extra proton causes the atomic number to increase by1 but has no effect on the mass number. Be able to balance the nuclear equations like you did on the worksheets. 35) In a fission reaction, an atom’s nucleus is broken down. 36) In a fusion reaction, two nuclei are fused (put together) to make a larger nucleus. 37) Both fusion and fission reactions release a lot of energy, much more than any chemical reaction can release. 4 38) Half-life is how long it takes for half of the substance to decay into another substance in a nuclear reaction. 39) If a 200 g sample of an isotope has a half-life of 30 years. In 90 years there will be 25 g of it left. (not in answer bank) 5