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The Atom & Periodic Table Unit 2 Topics 1-3 Development of the Atomic Model Topic 1 • What do you think of when you hear the word ‘atom’? Lab: Black Box Atoms are so small we have special microscopes to see them. pictures of groups of carbon were MODEL TOPIC 1These – DEVELOPMENT OF THEatoms ATOMIC EXPLAIN taken with a TEM (Tunneling Electron Microscope) and an mallest particle ofsmall an element that(Atomic retains Force its properties. How isAFM an atom? Microscope). s are so small we have special microscopes Notice the scale bar (small black line in lower e them. right of picture). That line represents 2 nm (that’s 2 nanometers.) e pictures of groups of carbon atoms were If one nanometer equals 1x10-9 meters… with a TEM (Tunneling Electron oscope) and an AFM (Atomic Force oscope). AFM 2 nm Then 62,500,000 of these pictures would fit in one meter! That’s REALLY small!! Important Experiments You Need to Know: TEM Notice the scale bar (small black line in lower -9 One nanometer equals 1x10 meters. Discovering Electrons – right of picture). That line represents 2 nm (that’s 2 nanometers.) Negative Charge -9 in one meter! Then 62,500,000 of these pictures would fit If one nanometer equals 1x10 meters… Thomson (1897): Experimented with Cathode Then 62,500,000 of these pictures would fit in Ray Tubes (CRTs) Democritus's Atomic Theory The smallest piece of matter is indivisible (atomos, which means 'not to be cut') Atoms: • small • hard particles • made of the same material • always moving • capable of joining together Dalton’s Atomic Theory (1808) Matter is composed of extremely small particles called atoms, which cannot be subdivided, created, or destroyed. Thompson’s Atomic Theory (1904) • electrons (plums) evenly distributed throughout a positively charged ‘pudding’. Rutherford’s Atomic Theory (1911) Gold Foil Experiment Expected vs. Actual Rutherford’s Atomic Theory (1911) Gold Foil Experiment - Results 1. Atoms are MOSTLY EMPTY SPACE 2. In the atom is a DENSE, POSITIVELY CHARGED NUCLEUS Bohr’s Atomic Theory (1913) Planetary Model Atoms travel in specific orbits around the nucleus. Quantum Mechanical (Modern) Theory Electrons travel in diffuse clouds around the nucleus (orbitals) 13) An atomsymbol of oxygen is in an excited state. with Whenaan electron this atom moves from the third 29) Which represents a particle total of 10in electrons? shell to the second shell, energy is 1) Al 2) N3+ 3) N 4) Al3+ 1) absorbed by the electron 3) emitted by the electron 57) 2) The modern model of the atom is were based conducted on the work ofdetermine emitted the nucleus 4) toabsorbed by the 30) In the earlyby1900s, experiments thenucleus structure of the atom. One o 14) these involved bombarding gold with alphainparticles. alpha particles 1) many overofavalence short period of time What isexperiments thescientists total number electrons in anfoil atom of sulfur the groundMost state? passed Some, however, deflected at various 2) 6one directly scientistthrough over a short period of time 1) 2)the 8 foil. 3) were 3 4) 4 angles. Based on th 15) In the box below, draw a Lewis electron-dot diagram of a selenium atom in the ground state. two conclusions alpha particle experiment, state that were made concerning the structure of a 3) many scientists over a long period of time atom. 4) one scientist over a long period of time Regents Practice 58) In the wave-mechanical model, an orbital is a region of space in an atom where there is 1) a high probability of finding an electron 31) The the atom shows that electrons are 2) amodern circularmodel path inofwhich neutrons are found 1) in regions orbitals are found 3) found a circular path in called which electrons 4) orbiting a high probability of finding a neutron 2) the nucleus in fixed paths located in sphere 59) 3) An electron hasa asolid charge of covering the nucleus 4) with neutrons inathe nucleus 1) combined +1 and a smaller mass than proton 3) -1 and a smaller mass than a proton How many electrons are contained in an Au3+ ion? 2) +1 and the mass as a proton 4) has -1 and the same mass as a proton 32) 1) Compared to asame calcium atom, 82 2) 197 the calcium ion Ca 3) 2+ 76 4) 79 16) 60) What Which is based on the "gold experiment" the protons resulting model of the atom? 1) more 3) and more 17) is conclusion theelectrons total number of neutrons in anfoil atom of aluminum-27? 1) fewer An atom has hardly any empty space, and the nucleus has a negative charge. 2) protons 4) fewer electrons 2) An atom is mainly empty space, and the nucleus has a negative charge. 33) When a lithium atom forms an Li+ ion, the lithium atom 3) An atom is electron mainly empty and theshell nucleus a positive charge. 18) Compared to an in the space, first electron of an has atom, an electron in the third shell of 1) loses a proton 3) gains an electron 4) same An atom has has a positive charge. the atom hashardly any empty space, and the nucleus 2) less gains a proton 4) mass loses an electron 1) mass 3) less 4) more energy Questions 61energy through 63 refer2)to more the following: 19) In the modern wave-mechanical model of the atom, the orbitals are regions of the most probable location of model of the atom, each atom is composed of three major subatomic (or fundamental) In the modern 1) electrons 2) protons 3) positrons 4) neutrons particles. 20) Which electron transition represents a gain of energy? 1) from 2nd to 3rd shell 3) from 3rd to 1st shell 2) from 2nd to 1st shell 4) from 3rd to 2nd shell UNIT 2 TOPIC 2 – SUBATOMIC PARTICLES & SYMBOLS ENGAGE Subatomic Particles & Symbols Topic 2 He Be Helium Beryllium 2 protons 4 protons 2 neutrons electrons orbit 5 neutrons 2 electrons protons + neutrons in the nucleus 4 electrons # of protons = # of electrons different # of protons from neutrons? Subatomic Particles & Properties Particle Symbol Location Electron e- Outside nucleus Proton p+ Neutron n0 Electrical Charge Approximate Actual Mass Relative (g) Mass (amu) 1- 1/1840 (essentially 0) 9.11 x 10-28 Inside nucleus 1+ 1 1.67 x 10-24 Inside nucleus 0 1 1.67 x 10-24 What does the unit ‘amu’ mean? atomic mass unit (1/12 of the mass of a carbon-12 atom) _____________________________________________ neutral ATOMS are electrically ______________ . This means protons must equal the that the number of ___________ electrons . number of ______________ Get out your Reference Tables!! Atomic Mass 12.011 Symbol Atomic Number Electron Configuration 6 C -4 +2 +4 2-4 Atomic Number: # of protons in the nucleus Atomic Mass: # of protons + neutrons in the nucleus We’ll get to these later 1) 2) 3) 4) equal numbers of each isotope are present more isotopes have an atomic mass of 1 than of 2 or 3 isotopes have only an atomic mass of 1 more isotopes have an atomic mass of 2 or 3 than of 1 37) What is the electron configuration of a sulfur atom in the ground state? 1) 2-6 2) 2-4 3) 2-8-6 4) 2-8-4 25) What is the total number of valence electrons in an atom of electron configuration X? 38) When compared with the energy of an electron in the first shell of a carbon atom, the energy of an electron in the second shell of a carbon atom is 1) the same 2) less 3) greater 26) What electron configuration represents the excited state of a calcium atom? 39) Which notation represents an atom of sodium with an atomic number of 11 and a mass number of 24? Regents Practice 2) 3) 1) atomic mass of an element The is the weighted average of the masses of 4) 1) all of its radioactive isotopes 3) all of its naturally occurring isotopes 3+ 40) 2) What the least total number of isotopes electrons in a Cr ion? 4) its two most abundant isotopes itsistwo abundant 1) 21 2) 27 3) 24 4) 18 ? 28) What is the mass number of the nuclear symbol 41) In which of the following pairs do the particles have approximately the same mass? 1) 28 2) 10 19 4) 9 1) neutron and beta particle 3) 3)neutron and electron 2) proton and represents electron and neutron 29) Which symbol a particle with a total of4)10proton electrons? 5718 42) 1) Which two notations represent atoms that are isotopes of the same element? 3+ 3+ Al 2) N 3) N 4) Al 12) 1) Which statement is true about a proton and3)an electron? and andthe structure of the atom. One of 30) In the early 1900s, experiments were conducted to determine 1) They have different and gold different charges. these experiments involvedmasses bombarding foil with alpha particles. Most alpha particles 2) They havethrough different andhowever, the same passed directly themasses foil. Some, were deflected at various angles. Based on this 2) and 4) charges. and twoand 3) They have the same state masses different charges. alpha particle experiment, conclusions that were made concerning the structure of an atom. 4) They have the same masses and the same charges. 43) What is the total number of electrons in an S2- ion? 13) An atom of oxygen is in an excited state. When an electron in this atom moves from the 1) 18 2) 16 3) 14 4) 10 shell to the second shell, energy is 31) The modern model of theapproximately atom shows that are 44) Which two particles have the electrons same mass? 27) 47) 2) A student measured the wavelength of hydrogen's visible red line to be 647 nanometers. and 4) spectral and Based on the information in the reading passage, show a correct numerical setup for calculating 5718 - 1 - Page 9 the student's percent error. Questions 83 and 84 refer to the following: 43) What is the total number of electrons in an S2- ion? The shows of selected elements. 1) 18 below 2)spectra 16 states 3) 14 4) 10 48) diagram Explain, in terms of bright-line electron energy and energy changes, how hydrogen's bright-line spectrum is produced. 44) Which two particles have approximately the same mass? 1) neutron and positron 3) neutron and electron proton neutron present on the surface of a star can 4) beproton andusing electron 49) 2) Explain howand the elements identified bright-line Regents Practice spectra. 45) The atomic number of an atom is always equal to the number of its 1) protons plus electrons 3) neutrons, only 83) Explain how a bright-line spectrum is produced, in terms of excited state, energy transitions, 2) protons plus neutrons 4) protons, only and ground state. 50) Which ion has the same electron configuration as an atom of He? 1) O22) Ca2+ 3) H - 51) Identify What is the the two total numberin ofthe electrons found in spectrum. an atom of sulfur? 84) elements given unknown 1) 16 2) 6 3) 32 4) Na+ 4) 8 52) Which statement best describes electrons? 85) Which diagram represents the nucleus of an and atomare of found?in the nucleus. 1) They are negative subatomic particles 2) They are positive subatomic particles and are found in the nucleus. 3) They are negative subatomic particles and are found surrounding the nucleus. 1) 2) 4) 4) They are positive subatomic particles and are3) found surrounding the nucleus. 53) In the box below, draw a Lewis electron-dot diagram for a sulfur atom in the ground state. 86) In the box below, draw a Lewis electron-dot structure for an atom of phosphorus. Look at the following sample of 100 Neon atoms in the “Jazz” sign. How many different types of Neon atoms are there in the sample? What is different about them? Which type is most abundant? Which type is least abundant? Isotopes Find Neon on the Periodic table and look at its Atomic Mass. What connection can Topic 3 you make between Neon’s Atomic Mass and this sample of atoms? Notation of Atoms 35Cl Cl-35 Chlorine-35 Chlorine - 35 Chlorine - 37 17 p 18N 17 p 20N Isotopes (Iso-, meaning same) Atoms with same # of protons, different # of neutrons What are three things that are the same between atoms that are isotopes? 1. Same chemical properties 2. Same atomic number 3. Same number of electrons What are two things that are different? 1. Different number of neutrons 2. Different mass numbers otopes = ___________________________________________________________ … What are three things that are the same between atoms that are isotopes? 1. Remember! 2. 3. What are two things that are different? 1. Number of protons 2. defines the element. emember!!! Number of neutrons 1. The number of protons defines the element. determines the isotope 2. The number of neutrons determines which isotope of a given element you have. However, their atomic masses are not the same because the number of neutrons of the atomic nucleus of each isotope varies. In the case of helium, both isotopes have two protons in their nuclei. However, helium-3 has one neutron, while helium-4 has two neutrons. Table 4 lists the four stable isotopes of lead. The least abundant of these isotopes is lead-204, while the most common is lead-208. Why do all lead atoms have 82 protons and 82 electrons? www.scilinks.org Topic : Atoms and Elements SciLinks code: HW4017 Lead’s Isotopes Table 4 The Stable Isotopes of Lead Name of atom Symbol Number of neutrons Mass number Mass (kg) Abundance (%) Lead-204 204 82Pb 122 204 203.973 1.4 Lead-206 206 82Pb 124 206 205.974 24.1 Lead-207 207 82Pb 125 207 206.976 22.1 Lead-208 208 82Pb 126 208 207.977 52.4 Chapter 3 Atomic Mass: given to a number of decimal places. This is because, in most cases, there are a number of naturally occurring isotopes. Copyright © by Holt, Rinehart and Winston. All rights reserved. Mass Number: the number of protons and neutrons in the isotope. 2. Look at a Periodic Table....Atomic mass is given to a number of decimal places. This is because, in most cases, there are a number of naturally occurring isotopes. Mass vs. Mass Number Atomic Isotope Hydrogen-1 Hydrogen-2 (deuterium) Hydrogen-3 (tritium) Atomic Number of Number of Number of Number Protons Neutrons Electrons Mass Number (amu) 1 1 0 1 1 1 1 1 1 2 1 1 2 1 3 Hydrogen three isotopes. = 1.0079 amu) Hydrogen has threehas isotopes, each with a whole(Atomic number formass a mass number. Yet, hydrogen as an element has an atomic mass on the periodic table of1.0079 1.0079 amu. Based this information, Which isotope on of hydrogen must be the mostwhich abundant, based on this data? ____ isotope must be the most abundant? H Write it in correct notation.____________________________________________ 1 For example: Hydrogen has three isotopes, each with a whole number for a mass number. Yet, hydrogen as an element has an atomic mass on the periodic table of 1.0079 amu. Which isotope of hydrogen must be the most abundant, based on this data? ____ WriteExample it in correct notation.____________________________________________ For example: A natural sample of C (atomic mass = 12.011 amu) is a mixture of C-12 (98.89%) and C-14 (1.11%). 6 has an average atomic mass of __________ 12.011 amu, Carbon's atomic number is ______, 12 amu. and carbon's most common isotope has a mass number of ______ 6 protons, ______ 6 Therefore, the most common type of carbon atom has _______ 6 electrons. Another naturally-occurring isotope of carbon is Cneutrons and ______ 14, but it is rare in comparison to the amount of C-12 in nature. 13) An atom of oxygen is best in an excitedanstate. 6) Which of these phrases describes atom?When an electron in this atom moves from the thir best 6) shell Which these phrases describes an atom? embedded toofthe second energy is uniformly 1) a hard sphere withshell, positive particles 1) aaabsorbed hardsphere sphere with positive particles uniformly embedded 2) hard negative particles uniformly embedded by with the electron 3) emitted by the electron 2) aaemitted hard sphere negativeby particles uniformly embedded 3) positive nucleus surrounded a cloud of negative charges 2) by thewith nucleus 4) absorbed by the nucleus 4) surrounded by aby hard negative shell 3) aapositive positivenucleus nucleus surrounded a cloud of negative charges 5718 - 1 - Page 14) What is the total number of valence electrons in an atom of sulfur in the ground state? 4) a positive surrounded by aofhard negative shellin an atom 7) Which According to thenucleus wave-mechanical model the atom, electrons 24) radioisotope is used in medicine to treat thyroid disorders? 1) 6 2) 8 3) 3 4) 4 1) have a positive charge 7) Regents Practice According to the wave-mechanical model of the atom, in an atom 1) uranium-238 3)electrons cobalt-60 2) the are box located in orbitals outside nucleus 15) In below, draw a Lewisthe electron-dot diagram of a selenium atom in the ground state 1) have a positive charge 2) iodine-131 4) phosphorus-32 3) are most likely found in an excited state 2) are located in orbitals outside the nucleus Questions 25 and 26 refer to the following: 4) travel in defined circles 3) are most likely found in an excited state 8) What is the total number of neutrons in the nucleus of a neutral atom that has 19 electrons and a 4) travel in defined circles 8) 9) mass number of 39? What neutrons in the nucleus has 19 electrons and a 1) 19 is the total number 2) of20 3) 58of a neutral atom that 4) 39 mass number of 39? What is the mass number of an atom that has six protons, six electrons, and eight neutrons? 1) 19 2) 20 3) 58 4) 39 1) 6 2) 20 3) 14 4) 12 9) What is the number of an atom 10) Compared to mass a proton, an electron has that has six protons, six electrons, and eight neutrons? 1) the 6 issame 2) 20 the electrons 14of electron configuration 4) 12X? 25) What the total number of valence in an3) atom 1) quantity of charge and opposite sign 16) electrons contained in ansign Au3+ ion? 2) themany sameto quantity ofare charge and the same 10) How Compared a proton, an electron has 3) a82 greater quantity of charge the same sign 1) 2) and 197 1) the same quantity of charge and the opposite sign 3) 76 26) 17) 4) a greater quantity of charge and the opposite sign 4) 79 What electron configuration the of a calcium atom? 14 2) the quantity of charge and thein same sign ofstate What issame the total number of represents neutrons anexcited atom aluminum-27? 11) Which electron configuration represents an atom of chlorine in an excited state? 3) a greater quantity of charge and the same sign 1) 2-8-8 and the opposite 3) sign 2-8-7 4) 2-8-6-1 4) 2-8-7-1 a greater quantity of2)charge 27) atomic massconfiguration an element is the weighted average of theinmasses of state? 11) The Which electron represents an atom of chlorine anan excited 18) Compared to an of electron in the first electron shell of an atom, electron in the third shell 1) of its radioactive isotopes 3) 2-8-7 all of its naturally occurring isotopes 1) all 2-8-7-1 2) 2-8-8 3) 4) 2-8-6-1 the same atom has 2) its two least abundant isotopes 4) its two most abundant isotopes 28) 1) less energy 2) more mass What is the mass number of the nuclear symbol ? 3) less mass 4) more ener 19) In the modern wave-mechanical model of the atom, the orbitals are regions of the most prob Topic 3 - Review Isotopes: Same protons, different neutrons Mass Number: # of protons and neutrons in an isotope Atomic Mass: Given in decimal form, showing that more than one isotope can be present Bohr & Lewis Dot Structures for Electrons in Atoms