Chapter 1A Matter and Atomic Structure Past Paper (2024)

CHEMISTRY.  MATTER AND ATOMIC STRUCTURE CHAPTER 1A CHEMISTRY, 11E 2  CHAPTER 1A OUTLINE 1. Classification of matter 2. Dalton’s atomic theory 3. The structure of the atom 4. Atomic number, mass number and isotopes 5. Ions 6. Chemical Formula 7...

CHEMISTRY.  MATTER AND ATOMIC STRUCTURE CHAPTER 1A CHEMISTRY, 11E 2  CHAPTER 1A OUTLINE 1. Classification of matter 2. Dalton’s atomic theory 3. The structure of the atom 4. Atomic number, mass number and isotopes 5. Ions 6. Chemical Formula 7. Chemical Nomenclature 8. Molecular compound 9. Relative mass 10. Mass spectrometer 3  LEARNING OBJECTIVES: Define and classify matter as substance or mixtures. Differentiate between homogeneous and heterogeneous mixtures. Categorize substance as elements or compounds. Outline Dalton’s hypotheses about nature of matter. Define and describe the physical properties of electrons, protons and neutrons. Explain the nature of isotopes and use mass number of an isotope to calculate number of electrons, protons or neutrons. Identify ions. Determine formulas of ionic compounds. 4  LEARNING OBJECTIVES (CONTINUE..): Chemical nomenclature to name the different types of compounds including ionic compound, molecular compounds and oxoacids. Describe chemical formula and molecular models. Determine the average atomic mass of an element and average molar mass of a substance. Describe the components of mass spectrometer. Calculate the relative atomic mass from mass spectrum of an element and molecular element. 5 1.0 CLASSIFICATION OF MATTER Anything that occupies space and has mass. 1.0 CLASSIFICATION OF MATTER 7 1.0 CLASSIFICATION OF MATTER MATTER Stuff that has mass and takes up space (Pure) Substances Mixtures has a definite (constant) composition and Physical combinations of two or distinct properties) more substances Elements Compounds Homogeneous Heterogeneous Examples: iron Examples: water, Uniform throughout, Not uniform throughout, sulfur, carbon, salt, sugar aka “solution”; distinct pieces; Hydrogen, oxygen can be decomposed Think: smoothie Think: fruit salad to simpler substances can not be because it is made up decomposed to of more than one simpler substances. element. 1.0 CLASSIFICATION OF MATTER MATTER is anything that has mass and takes up space.  CLASSIFICATION OF MATTER BASED ON COMPOSITION Atoms are the building blocks of matter. Each element is made of a unique kind of atom but can be made of more than one atom of that kind. Note: Balls of different colors are used A compound is made of to represent atoms of different atoms from two or more elements. Attached balls represent connections between atoms that are different elements. seen in nature. These groups of atoms are called molecules. 1.0 CLASSIFICATION OF MATTER ELEMENTS AND COMPOSITION There are currently 118 named elements. Only five elements make up 90% of the earth’s crust by mass. Only three elements make up 90% of the human body by mass! Note the importance of oxygen!  Describe matter in terms of atoms JOHN DALTON DALTON’S ATOMIC THEORY (PROPOSED IN 1808): All elements are made of tiny atoms. Atoms cannot be subdivided. Atoms of the same element are exactly alike. Atoms of different elements can join to form molecules. Law of Conservation of Mass – mass cannot be created or destroyed, although it may be 13 rearranged. 16 X + 8Y 8 X2Y Law of Conservation of Mass All neutral atoms can be identified by number of protons and neutrons. Proton has a positive charge. Neutron has no charge. Electron has a negative charge.  Particle Mass Charge* Electron 9.109 × 10−31 kg 1− Proton 1.673 × 10−27 kg 1+ Neutron 1.675 × 10−27 kg None *The magnitude of the charge of the electron and the proton is 1.60 × 10−19 C. 4.0 ATOMIC NUMBER, MASS NUMBER AND ISOTOPES Proton number (Z) → number of proton in the nucleus of the atom of an element → also known as atomic number Nucleon number (A) → total number of proton and neutrons present in the nucleus of the atom of an element → also known as mass number Nucleon Number A ZX Element Symbol Proton Number 4.0 ATOMIC NUMBER, MASS NUMBER AND ISOTOPES ⚫ Isotopes are two or more atoms of the same element that have the same proton number in their nucleus but different nucleon number. 1 1H 2 1H 3 1H 238 92 U 235 92 U 4.0 ATOMIC NUMBER, MASS NUMBER AND ISOTOPES 19  4.0 ATOMIC NUMBER, MASS NUMBER AND ISOTOPES Isotopes react in the same way because they have the same numbers of electrons, →chemical reactions depend only on the number and arrangement of electrons and → not on the composition of the nucleus. Example, both protium and deuterium would react in the same way with nitrogen: Isotopes have different physical properties because, →different masses mean that their atoms move at different speeds. →The boiling point of 11𝐻 2 is -253°C, whereas that of 21𝐻 2 is -250°C. →Heavy water (D2O) has a melting point of 3.8°C and a boiling point of 101.4°C The isotopes of an element with fewer neutrons will have: Lower masses faster rate of diffusion 20 Lower densities lower melting and boiling points 4.0 ATOMIC NUMBER, MASS NUMBER AND ISOTOPES Do You Understand Isotopes? How many protons, neutrons, and electrons are in 146 C ? 6 protons, 8 (14 - 6) neutrons, 6 electrons How many protons, neutrons, and electrons are in 116 C ? 6 protons, 5 (11 - 6) neutrons, 6 electrons 21 Which of the following statements are true? I.The number of protons is the same for all neutral atoms of an element II.The number of electrons is the same for all neutral atoms of an element III.The number of neutrons is the same for all neutral atoms of an element A. I, II, and III are true B. Only I and II are true C. Only II and III are true D. Only I and III are true E. I, II, and III are false 22 5.0 IONS A positive ion (cation) is formed when an atom loses (an) electron(s) so that the ion has more protons(+) than electrons(-) A negative ion (anion) is formed when an atom gains (an) electron(s) so that the ion has more electrons(-) than protons(+) 23 5.0 IONS (MONOATOMIC ION) A monatomic ion contains only one atom When an atom of a group of atoms loses or gains electrons, it becomes an ion. Cations are formed when at least one electron is lost. Monatomic cations are formed by metals. Anions are formed when at least one electron is gained. Monatomic anions are formed by nonmetals, except the noble gases. 5.0 IONS Do You Understand Ions? 27 3 + How many protons and electrons are in 13 Al ? 13 protons, 10 (13 – 3) electrons How many protons and electrons are in 78 34 Se 2- ? 34 protons, 36 (34 + 2) electrons 25 6.0 CHEMICAL FORMULA ▪ Ionic compounds consist of a combination of cations and an anions ▪ Ionic compounds (such as NaCl) are generally formed between metals and nonmetals. ▪ Electrons are transferred from the metal to the nonmetal. The oppositely charged ions attract each other. Only empirical formulas are written. ▪ the sum of the charges on the cation(s) and anion(s) in each formula unit must equal zero The ionic compound NaCl How is an ion formed? A. By either adding or subtracting protons from the atom B. By either adding or subtracting electrons from the atom C. By either adding or subtracting neutrons from the atom D. All of these are true E. Two of these are true 27 (POLYATOMIC ION) A polyatomic ion contains more than one atom 28  WRITING FORMULAS Because compounds are electrically neutral, one can determine the formula of a compound this way: – The charge on the cation becomes the subscript on the anion. – The charge on the anion becomes the subscript on the cation. – If these subscripts are not in the lowest whole-number ratio, divide them by the greatest common factor. 29 Formula of Ionic Compounds 2 x +3 = +6 3 x -2 = -6 Al2O3 Al3+ O2- 1 x +2 = +2 2 x -1 = -2 CaBr2 Ca2+ Br- 2 x +1 = +2 1 x -2 = -2 Na2CO3 Na+ CO32- 30 7.0 CHEMICAL NOMENCLATURE The system of naming compounds is called chemical nomenclature. We will learn how to name: 1) Ionic compounds 2) Covalent compounds 3) Acids 4) Binary molecular compounds 5) Simple organic compounds – Alkanes – Alcohols 32 7.0 CHEMICAL NOMENCLATURE IONIC COMPOUNDS often a metal + nonmetal Cation is always named first and the anion second Monatomic cation takes its name from the name of the parent element Monatomic anion is named by taking the root of the element name and adding -ide anion (nonmetal), add “ide” to element name Cation Name Anion Name H+ Hydrogen H− Hydride Name each binary compound a. CsF Li+ Lithium F− Fluoride b. AlCl3 Na+ Sodium Cl− Chloride c. LiH K+ Potassium Br− Bromide Cs+ Cesium l− Iodide Be2+ Beryllium O2− Oxide a. CsF is cesium fluoride Mg2+ Magnesium S2− Sulfide b. AlCl3 is aluminum chloride c. LiH is lithium hydride Ca2+ Calcium N3− Nitride Ba2+ Barium P3− Phosphide Al3+ Aluminum Common Monatomic Cations and Anions 7.0 CHEMICAL NOMENCLATURE A close up of text on a white background Description automatically generated 34  7.0 CHEMICAL NOMENCLATURE Transition metal ionic compounds A close up of text on a white background Description automatically generated 35  NAMING TYPE COMPOUNDS 1. GIVE THE SYSTEMATIC NAME FOR EACH OF THE FOLLOWING COMPOUNDS: A. CUCL B. HGO C. FE2O3 2. GIVEN THE FOLLOWING SYSTEMATIC NAMES, WRITE THE FORMULA FOR EACH COMPOUND: a. MANGANESE(IV) OXIDE b. LEAD(II) CHLORIDE More Example: 37 38 7.0 CHEMICAL NOMENCLATURE 39  NOMENCLATURE OF BINARY MOLECULAR COMPOUNDS (INORGANIC COMPOUNDS) THE NAME OF THE ELEMENT FARTHER TO THE LEFT IN THE PERIODIC TABLE (CLOSER TO THE METALS) OR LOWER IN THE SAME GROUP IS USUALLY WRITTEN FIRST. A PREFIX IS USED TO DENOTE THE NUMBER OF ATOMS OF EACH ELEMENT IN THE COMPOUND (MONO- IS NOT USED ON THE FIRST ELEMENT LISTED, HOWEVER). Prefix Number Indicated mono- 1 di- 2 tri- 3 tetra- 4 penta- 5 hexa- 6 hepta- 7 octa- 8 nona- 9 deca- 10 41  INTERACTIVE EXAMPLE 1. NAME EACH OF THE FOLLOWING COMPOUNDS: a. PCL5 b. PCL3 c. SO2 2. FROM THE FOLLOWING SYSTEMATIC NAMES, WRITE THE FORMULA FOR EACH COMPOUND: a. SULFUR HEXAFLUORIDE b. SULFUR TRIOXIDE c. CARBON DIOXIDE The “-ide” Nomenclature of Some Common Monoatomic Anions According to Their Positions in the Periodic Table 44 NOMENCLATURE OF BINARY COMPOUNDS THE ENDING ON THE SECOND ELEMENT IS CHANGED TO -IDE. – CO2: CARBON DIOXIDE – CCL4: CARBON TETRACHLORIDE If the prefix ends with a or o and the name of the element begins with a vowel, the two successive vowels are often elided into one. – N2O5: DINITROGEN PENTOXIDE – CO: CARBON MONOXIDE Names and Formulas of Some Common Inorganic Cations & Anions 46  Some Polyatomic Ions NH4+ ammonium SO42- sulfate CO32- carbonate SO32- sulfite HCO3- bicarbonate NO3- nitrate ClO3- chlorate NO2- nitrite Cr2O72- dichromate SCN- thiocyanate CrO42- chromate OH- hydroxide 47 PATTERNS IN OXYANION NOMENCLATURE WHEN THERE ARE TWO OXYANIONS INVOLVING THE SAME ELEMENT – THE ONE WITH FEWER /WITH SMALLER OXYGENS ENDS IN -ITE. – THE ONE WITH MORE OXYGENS/LARGE NUMBER ENDS IN -ATE. NO2− : NITRITE; NO3− : NITRATE SO32− : SULFITE; SO42− : SULFATE POLYATOMIC IONS WHEN MORE THAN TWO OXYANIONS MAKE UP A SERIES: USE THE PREFIX HYPO- (LESS THAN) TO NAME MEMBERS OF THE SERIES WITH THE FEWEST O ATOMS USE THE PREFIX PER- (MORE THAN) TO NAME MEMBERS OF THE SERIES WITH THE MOST O ATOMS PATTERNS IN OXYANION NOMENCLATURE 50  INTERACTIVE EXAMPLE -NAMING COMPOUNDS CONTAINING POLYATOMIC IONS 1. GIVE THE SYSTEMATIC NAME FOR EACH OF THE FOLLOWING COMPOUNDS: a. NA2SO4 C. FE3(NO3)3 E. NA2SO3 b. KH2PO4 D. MN(OH)2 F. NA2CO3 2. GIVEN THE FOLLOWING SYSTEMATIC NAMES, WRITE THE FORMULA FOR EACH COMPOUND: a. SODIUM HYDROGEN CARBONATE D. SODIUM SELENATE b. CESIUM PERCHLORITE E. POTASSIUM BROMATE c. SODIUM HYPOCHLORITE  ACID NOMENCLATURE IF THE ANION IN THE ACID ENDS IN -IDE, CHANGE THE ENDING TO -IC ACID AND ADD THE PREFIX HYDRO-. – HCL: HYDROCHLORIC ACID – HBR: HYDROBROMIC ACID – HI: HYDROIODIC ACID If the anion ends in -ate, change the ending to -ic acid. – HClO3: chloric acid – HClO4: perchloric acid If the anion ends in -ite, change the ending to -ous acid. – HClO: hypochlorous acid – HClO2: chlorous acid  Names of Oxoacids and Oxoanions that contain Chlorine Names of Acids* That Do Names of Some Oxygen-Containing Acids Not Contain Oxygen 53 NOMENCLATURE OF ORGANIC COMPOUNDS: ALKANES Organic chemistry is the study of carbon. Organic chemistry has its own system of nomenclature. The simplest hydrocarbons (compounds containing only carbon and hydrogen) are alkanes. The first part of the names just listed correspond to the number of carbons (meth- = 1, eth- = 2, prop- = 3, etc.). It is followed by -ane. NOMENCLATURE OF ORGANIC COMPOUNDS: ALCOHOLS When a hydrogen in an alkane is replaced with something else (a functional group, like –OH in the compounds above), the name is derived from the name of the alkane. The ending denotes the type of compound. – An alcohol ends in -ol. NOMENCLATURE OF ORGANIC COMPOUNDS: ALCOHOLS When two or more molecules have the same chemical formula, but different structures, they are called isomers. 1-propanol and 2- propanol have the oxygen atom connected to different carbon atoms, but both have the formula c3h8o. 8.0 MOLECULAR COMPOUNDS Molecular compounds are composed of molecules and almost always contain only nonmetals. A molecule consists of two or more atoms in a definite arrangement held together by chemical bonds. H2 H2O NH3 CH4 A diatomic molecule contains only two atoms H2, N2, O2, Br2, HCl, CO A polyatomic molecule contains more than two atoms O3, H2O, NH3, CH4 8.0 MOLECULAR COMPOUNDS HI hydrogen iodide NF3 nitrogen trifluoride SO2 sulfur dioxide N2Cl4 dinitrogen tetrachloride TOXIC! NO2 nitrogen dioxide Laughing Gas N2O dinitrogen monoxide 58 8.0 MOLECULAR COMPOUNDS 59  9.0 RELATIVE MASS Relative Atomic Mass (RAM) Relative Molecular Mass (RMM) 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑚𝑎𝑠𝑠𝑒𝑠 𝑜𝑓 one 𝑎𝑡𝑜𝑚 𝑜𝑓 𝑎𝑛 𝑒𝑙𝑒𝑚𝑒𝑛𝑡 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑚𝑎𝑠𝑠𝑒𝑠 𝑜𝑓 𝑜𝑛𝑒 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑒 𝑜𝑓 𝑎 𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑 𝑅𝐴𝑀 = 𝑅𝑀𝑀 = 1 1 𝑜𝑓 𝑎𝑡𝑜𝑚 𝑜𝑓 𝑐𝑎𝑟𝑏𝑜𝑛 12 𝑜𝑓 𝑎𝑡𝑜𝑚 𝑜𝑓 𝑐𝑎𝑟𝑏𝑜𝑛 12 12 12 60 61 62 10. MASS SPECTROMETER The mass of an atom cannot be measured directly. A mass spectrometer is an instrument used to measure the precise masses and relative quantity of atoms and molecules. Schematic diagram: A mass spectrometer shows a large glass tube curving upward and closed at one end.  USES OF MASS SPECTROMETER HELPS DETERMINE ACCURATE MASS VALUES FOR INDIVIDUAL ATOMS DETERMINES THE ISOTOPIC COMPOSITION OF NATURAL ELEMENTS MASS SPECTROMETER – 5 STAGES Once the sample of an element has been placed in the mass spectrometer, it undergoes five stages. Vaporisation – the sample has to be in gaseous form. If the sample is a solid or liquid, a heater is used to vaporise some of the sample. X (s) → X (g) or X (l) → X (g) MASS SPECTROMETER – 5 STAGES Ionization – sample is bombarded by a stream of high-energy electrons from an electron gun, which ‘knock’ an electron from an atom. This produces a positive ion: X (g) → X + (g) + e- Acceleration – an electric field is used to accelerate the positive ions towards the magnetic field. The accelerated ions are focused and passed through a slit: this produces a narrow beam of ions.  MASS SPECTROMETER – 5 STAGES Deflection – the accelerated ions are deflected into the magnetic field. The amount of deflection is greater when: the mass of the positive ion is less the charge on the positive ion is greater lighter ions with higher velocities and lower m/z values will be deflected more than heavier ions with lower velocities and higher m/z values the strength of the magnetic field is greater If all the ions are travelling at the same velocity and carry the same charge, the amount of deflection in a given magnetic field depends upon the mass of the ion. For a given magnetic field, only ions with a particular relative mass (m) to charge (z) ration – the m/z value – are deflected sufficiently to reach the detector.  MASS SPECTROMETER Detection – ions that reach the detector cause electrons to be released in an ion-current detector The number of electrons released, hence the current produced is proportional to the number of ions striking the detector. The detector is linked to an amplifier and then to a recorder: this converts the current into a peak which is shown in the mass spectrum. 69  Schematic Diagram Of Mass Spectrometer Acceleration chamber Vaporization chamber Magnetic field + Hot filament/ Ionization chamber Detector 70 In Summary, FYI The relative mass of atoms is determined by mass spectrometer. Vaporization chamber the sample is vaporized into gaseous atoms. Ionization chamber the gaseous atoms are ionized by a hot wire to become gaseous positive ions. Acceleration chamber the positive ions are accelerated by an electric field towards plate. Magnetic field the positive ions are then deflected. ions with small masses are deflected the most. The data will be printed as a mass spectrum of the element. The RAM of the ion can be calculated. 71  AVERAGE ATOMIC MASS KNOWN AS ATOMIC WEIGHT (AS PER IUPAC’S DECLARATION), WHICH IS DIMENSIONLESS BY CUSTOM IUPAC - INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY SINCE ELEMENTS OCCUR IN NATURE AS MIXTURES OF ISOTOPES, ATOMIC MASSES ARE USUALLY AVERAGE VALUES  EXAMPLE : AVERAGE MASS OF AN ELEMENT When a sample of natural copper is vaporized and injected into a mass spectrometer, the results shown in the graph are obtained − Use these data to compute the average mass of natural copper ▪ Mass values for 63Cu and 65Cu are 62.93 u and 64.93 u, respectively  Solution Where are we going? − To calculate the average mass of natural copper What do we know? − 63Cu mass = 62.93 u − 65Cu mass = 64.93 u How do we get there? − As shown by the graph, of every 100 atoms of natural copper, 69.09 are 63Cu and 30.91 are 65Cu  Solution − Thus, the mass of 100 atoms of natural copper is ( 69.09 atoms )  62.93 u   atom  +(30.91 atoms  )   64.93 u  atom  = 6355 u  − Average mass of a copper atom is 6355 u = 63.55 u/atom 100 atoms ▪ This mass value is used in doing calculations involving the reactions of copper Exp 1: Mass Spectrometer Isotopes of boron m/z value 11 10 Relative 18.7 81.3 abundance % Ar of boron = (11 x 18.7) + (10 x 81.3) (18.7 + 81.3) = 205.7 + 813 100 = 1018.7 = 10.2 100 Exp 2: Mass Spectrometer 77 Exp 3: Mass Spectrometer Exp 4: Mass Spectrometer MASS SPECTROMETER – QUESTIONS A MASS SPEC CHART FOR A SAMPLE OF NEON SHOWS THAT IT CONTAINS: 90.9% 20NE 0.17% 21NE 8.93% 22NE CALCULATE THE RELATIVE ATOMIC MASS OF NEON YOU MUST SHOW ALL YOUR WORKING! MASS SPECTROMETER – QUESTIONS 90.9% 20NE 0.17% 21NE 8.93% 22NE (90.9 x 20) + (0.17 x 21) + (8.93 x 22) 100 Ar= 20.18 Exp 5: Mass Spectrometer CALCULATE THE RELATIVE 52.3 ATOMIC MASS OF LEAD YOU MUST SHOW ALL YOUR WORKING! 23.6 22.6 1.5 204 206 207 208 m/e MASS SPECTROMETER – QUESTIONS 1.5% 204PB 23.6% 206PB 22.6% 207PB 52.3% 208PB (1.5 x 204) + (23.6 x 206) + (22.6 x 207)+(52.3 x 208) 100 306 + 4861.6 + 4678.2 + 10878.4 20724.2 100 100 Ar= 207.24 Exp 6: Mass Spectrometer EXAMPLE: FIND THE RELATIVE ATOMIC MASS (AR) OF NATURALLY OCCURRING LEAD FROM THE DATA BELOW. RECORD YOUR ANSWER TO THE NEAREST TENTH. Mass Spectrum of Pb Isotopic Relative % relative 6 mass abundance abundance 5.2 204 0.2 2 5 206 2.4 24 4 207 2.2 22 relative abundance 208 5.2 52 3 2.4 2.2 2 × 204 + 24 × 206 + 22 × 207 + 52 × 208 2 𝐴𝑟 = 100 1 0.2 𝐴𝑟 =207.2 0 203 204 205 206 207 208 209 mass/charge Figure: The Mass Spectrum of Naturally Occurring Lead Exp 7: Mass Spectrometer Mass Spectrum of Magnesium ⚫ The mass spectrum of Mg shows that Mg consists of 3 isotopes: 24Mg, 25Mg and 26Mg. ⚫ The height of each line is proportional to the abundance of each isotope. ⚫ 24Mg is the most abundant of the 3 isotopes. 84 How to calculate the relative atomic mass from mass spectrum? RAM is calculated using data from the mass spectrum. σ(𝐼𝑠𝑜𝑡𝑜𝑝𝑖𝑐 𝑚𝑎𝑠𝑠 𝑥 𝐴𝑏𝑢𝑛𝑑𝑎𝑛𝑐𝑒) 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑎𝑡𝑜𝑚𝑖𝑐 𝑚𝑎𝑠𝑠 = σ 𝐴𝑏𝑢𝑛𝑑𝑎𝑛𝑐𝑒 85 Question 1: Calculate the relative atomic mass of neon from the mass spectrum. 86 Question 2: Copper occurs naturally as mixture of 69.09% of 63Cu and 30.91% of 65Cu. The isotopic masses of 63Cu and 65Cu are 62.93 amu and 64.93 amu respectively. Calculate the relative atomic mass of copper. 87 Question 3: Naturally occurring iridium, Ir is composed of two isotopes, 191Ir and 193Ir in the ratio of 5:8. The relative isotopic mass of 191Ir and 193Ir are 191.021 amu and 193.025 amu respectively. Calculate the relative atomic mass of Iridium. 88  Mass Spectrum of Molecular Elements A sample of chlorine which contains 2 isotopes with nucleon number 35 and 37 is analyzed in a mass spectrometer. how many peaks would be expected in the mass spectrum of chlorine? 89  MASS SPECTROMETER 35Cl-35Cl 35Cl-37Cl 37Cl-37Cl 35Cl-35Cl+ 35Cl-37Cl+ A sample of chlorine which contains 2 isotopes with nucleon number 35 and 37 is analyzed in a mass spectrometer. how 37Cl-37Cl+ many peaks would be expected in the mass spectrum of chlorine? 35Cl+ 37Cl+