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Flashcards

Atomic Structures

mysticalfirefox English 63 cards

Cards in this deck (63)

  1. 1What are the smallest possible pieces of elements called?Elements are composed of atoms
  2. 2Name the particles present in the nucleus of an atom.In the nucleus of an atom one can find the nucleons. This consist of the protons and the neutrons.
  3. 3What are protons?The protons have a mass of 1 as well as a charge of +1 . They make up the atomic number and the atomic mass number.
  4. 4What does the atomic number of an atom represent?This represents the number of protons found in the nucleus of the atom. It is a specific number and characteristic of each and every element. Any changes made to this number would completely alter the element itself
  5. 5What are neutrons?The neutrons have a mass of 1 however they have no charge and are thus neutral. The neutrons offer the nucleus stability as the protons, given their positive charge, would repel one another, causing the nucleus to become unstable.
  6. 6What does the mass number of an atom represent?This represents the number of protons and neutrons found in the nucleus of the atom. A change made to this number, provided it occurs in the number of neutrons, would give rise to isotopes of the same element.
  7. 7What is an Isotope?The isotopes are atoms of the same element having the same number of protons (atomic mass), and electrons but a different number of neutrons (atomic mass number).
  8. 8Define the Relative Atomic Mass.The relative atomic mass of an element is the average mass of all the isotopes of an element compared to 1/12th of the mass of an atom of Carbon 12 (12C).
  9. 9How is the Relative Atomic Mass determined? Why is Carbon 12 used as reference?The relative atomic mass is determined by mass spectroscopy and carbon is used as a reference because of its volatile nature, abundance, and accuracy as the Carbon 12 (12C) isotope has a mass of exactly 12.
  10. 10In the natural state the element M of atomic number 14, consists of the isotopes 28M, 29M, 30M in the ratio 60:3:2, respecitively; (a) Calculate the relative atomic mass of element M, (b) How many electrons are present in an atom of element M?, (c) How many neutrons are present in each atom of element M?(a) The answer should be = 28.11
    (b) The answer should be = 14 electrons
    (c) 28M has 14 neutrons, 29M has 15 neutrons and 30M has 16 neutrons.
  11. 11The isotopic composition of a certain element X is 80.00% 24X and 10.00% 26X. What is the relative atomic mass of X?The answer should be = 24.30
  12. 12An element Z has 2 isotopes, 79Z and 81Z. The average atomic mass is 80. ExplainAnswer
  13. 13An element X has 2 isotopes, 16X and 18X. The average atomic mass is 16.2. ExplainAnswer
  14. 14Boron has 2 isotopes, 10B and 11B. In a natural sample of boron is 18.7% and the rest is 11B. Find the average atomic mass of Boron.Answer
  15. 15The atomic number of Chlorine is 17. Using the s,p notation, give the electron configuration of; (a) Cl atom (b) Cl- ion(a) The answer should be 1s2, 2s2 2p6, 3s2 3p5
    (b) The answer should be 1s2, 2s2 2p6, 3s2 3p6
  16. 16Iron consists of 2 isotopes of mass numbers 55 and 56 and whose relative abundances are 20% and 80% respectively. Calculate the relative atomic mass of iron, giving your answer to 3 significant figures.The answer should be = 55.8
  17. 17What are electrons?The electrons have a very negligible mass as well as a charge of -1. They are attracted to the positive nature of the nucleus and are thus located traveling around it in orbitals whilst spinning on their own axis. The outer electrons (valency electrons) govern the chemical reactivity of the atom.
  18. 18What is the maximum number of electrons the; (a) 1st shell (b) 2nd shell (c) 3rd shell (d) 4th shell?(a) The answer should be 2 electrons
    (b) The answer should be 8 electrons
    (c) The answer should be 18 electrons
    (d) The answer should be 32 electrons
  19. 19What is Aufbau's Principle?Electrons will always occupy the lowest energy sub-shell available.
  20. 20What is Hund's Rule?The subshells contain the maximum number of unpaired electrons. Thus, where there is a choice between orbitals of equal energy, they fill the orbitals singly as far as possible. This only applies when the orbital has exactly the same energy and helps to minimise the repulsion between electrons and in doing so makes the atom more stable.
  21. 21(a) How many electrons are held in; (i) an s-orbital (ii) a p-orbital (iii) a d-orbital (iv) an f-orbital (b) How would you describe the shape of (i) an s-orbital (ii) a p-orbital(a) The answer should be;
    (i) 2 (ii) 6 (iii) 10 (iv) 14
    (b) The answer should be;
    (i) Spherical (ii) Dumb-bell shaped
  22. 22(a) Explain why s-block, p-block, d-block and f-block in the periodic table are named in this way. (b) For the s-block and p-block elements, the number of the last subshell to be occupied is the same as the period number. Is this true of the d-block elements? Give examples of period 4 to explain your answer.(a) The letter assigned to the block shows into which type of orbital the last electron enters.
    (b) No. The period number is the number of shells in the atom. In period 4 the transition metals fill the 3d-subshell after the 4s has been filled. Therefore, although the atoms have 4 shells, the last electron enters a 3d subshell.
    For example:
    Sc: [Ar] 3d1, 4s2
    Ti: [Ar] 3d2, 4s2
    V: [Ar] 3d3, 4s2
    Cr: [Ar] 3d5, 4s1
  23. 23Are the phrases 'Transition Metal' and 'd-block element' interchangeable?No, all transition metals are d-block elements but not all d-block elements are transition metals. The definition of A d-block element is one which the last electron entered a d sub-shell while a transition metal is one which forms at least 1 ion with an incomplete d-subshell. Therefore Scandium and Zinc are d-block elements but not transition metals. Scandium only forms ions with a charge of +3 so that it has an empty d-subshell. Zinc only forms ions with a charge of +2 so that it has a full d-subshell.
  24. 24Define emission spectrum.Certain atoms and molecules emit light when they are supplied with heat or electrical energy. When this light is view through a spectroscope a number of coloured lines are seen. The emission spectrum involves electrons moving around the nucleus in stable orbitals without emitting energy. When the atom absorbs energy, electrons jump from a lower energy level orbital to a higher energy level orbital in which they are less stable and cannot remain. Therefore, the electrons return to a lower energy orbital and release their excess energy as light. Each spectral line is caused by electrons falling back from a certain high energy orbital to a certain lower energy orbital. The greater the energy differences between these orbitals the higher the frequency of the corresponding spectral lines.
  25. 25What does the atomic size depend on?It depends on the number of protons and the number of shells.
  26. 26Does to atomic size increase or decrease when moving across the periodic table from left to right? Why?When moving from left to right across a periodic table the atomic size decreases. This is due the shielding effect remaining the same but the number of protons increasing causing the nucleus to have a greater pull on the outer electrons
  27. 27Does the atomic size increase or decrease when moving across the period of the transition metals? Why?When moving from left to right across the period Transition Metals have electrons added to an inner orbital, the d-subshell. There is both an increase in the shielding effect as well as an increase in the number of protons in the nucleus. Thus these two factors essentially cancel each other out so, that the atomic size remains approximately the same.
  28. 28When moving down any particular group in the periodic table does the atomic size increase or decrease? Why?When moving down any particular group in the period table the atomic size increases due to an increase in the number of shells and shielding effect. The increase in size occurs even though there is an increase in the number of protons in the nucleus, as the number of shells and the shielding effect outweigh the force of the pull of the nucleus.
  29. 29(a) Give the full electronic configuration of; (i) Mg atom (ii) Mg2+ ion. (b) The ions Na+ and Al3+ are isoelectronic with Mg2+. Explain what the term isoelectronic means. (c) Arrange the ions Na+, Mg2+ and Al3+ in order of increasing radius starting with the smallest.(a) The answer should be;
    (i) Mg: 1s2, 2s2 2p6, 3s2
    (ii) Mg2+: 1s2, 2s2 2p6
    (b) Isoelectronic means that they have the same electronic configuration.
    (c) Al3+, Mg2+ and Na+
  30. 30The atomic number of Manganese (Mn) is 25; (a) Give the full electronic configuration of (i) Mn (ii) Mn2+ (iii) Mn3+, (b) Which of the above ions has the most stable electronic configuration? Why? (c) Manganese is classified as a transition metal. List 3 important properties of transition metals.(ai) Mn: 1s2, 2s2 2p6, 3s2 3p6 3d5, 4s2
    Mn2+: 1s2, 2s2 2p6, 3s2 3p6 3d5
    Mn3+: 1s2, 2s2 2p6, 3s2 3p6 3d4
    (b) Mn2+ has the most stable electronic structure due to its half full d-subshell.
    (c) The important properties of transition metals includes; They are hard and dense metals, they have more than 1 valency, they have coloured compounds and their metals and compounds can be used as catalysts.
  31. 31(a) Give the full electronic configuration of; (i) Fe atom, (ii) Fe2+ ion, (iii) Fe3+ ion (b) Which of the above species has the most stable electronic configuration? Why?(a) The answer should be;
    (i) Fe: 1s2, 2s2 3p6, 3s2 3p6 3d6, 4s2
    (ii) Fe2+: 1s2, 2s2 3p6, 3s2 3p6 3d6
    (iii) Fe3+: 1s2, 2s2 3p6, 3s2 3p6 3d5
    (b) Fe3+ has the most stable electronic configuration due to its half full d-subshell.
  32. 32The element copper has a relative atomic mass of 63.55. It has 2 isotopes, one with a mass of 63 and the other with a mass number of 65. Calculate the percentage composition of a normal isotopic sample of Copper.Answer
  33. 33In a natural sample, 69 Ga : 71 Ga = 3:2. Find the average atomic mas of galliumAnswer
  34. 34Find the average relative atomic mass of Zirconium given that , in a sample of the element, 51.5% is 90Zr, 11.2% is 91Zr, 17.1% is 92Zr, 17.4% is 94Zr and 2.8% is 96Zr.Answer
  35. 35Define Ionisation EnergyThe Ionisation Energy is a measure of the energy required to remove an electron from a gaseous atom or ion.
  36. 36Define the 1st Ionisation EnergyThe 1st Ionisation Energy is the energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to produce 1 mole of gaseous cations each having a charge of +1.
  37. 37Define the 2nd Ionisation EnergyThe 2nd Ionisation Energy is the energy required to remove 1 mole of electrons from 1 mole of gaseous ions, each having a charge of +1, to produce 1 mole of gaseous ions, each having a charge of +2.
  38. 38Are value of Ionisation Energy endothermic or ectothermic? Why?All values of the Ionisation Energy are positive (endothermic) as energy must be supplied to remove the electron(s).
  39. 39What are the factors which affect the size of the Ionisation Energy?1. The charge of the nucleus
    2. The distance of the electron from the nucleus
    3. The number of shells between the outer electrons and the nucleus
    4. Whether the electron is on its own in an orbital or paired with another electron
    5. Configuration of the outer shell
  40. 40Two elements A and B are in the same group of the Periodic Table. Their first four Ionisation Energies are; A: 740 1500 7700 10500 B: 900 1800 14800 21000 (a) To which group of the Periodic Table do A and B belong? (b) Briefly explain your answer to (a) (c) Which of the two elements has the larger atomic number? (d) Briefly explain your answer to (c) (e) Give the formula of the compound of A with; (i) Oxygen (ii) Hydrogen(a) A and B belong to Group II
    (b) This is because there is a large increase from the 2nd to the 3rd Ionisation Energy, showing that the third electron is in an inner shell.
    (c) A has a higher atomic number.
    (d) This is because the corresponding Ionisation Energies of A are smaller than those of B showing that the electron is further away from the nucleus. The greater distance from the nucleus and the greater shielding effect makes the attraction between the nucleus and the outer electron in A lower than that in B, even though it has more protons in its nucleus.
    (ei) AO (eii) AH2
  41. 41(a) Write equations representing; (i) The first ionisation Energy of Magnesium (ii) The first Ionisation Affinity of Chlorine (b) State whether each of the following statements is True or False; (i) The ions Li+ and Be2+ have the same electron configuration. (ii) The frist Ionisation Energy of Lithium is bigger than that of sodium. (iii) The first Ionisation Energy of Magnesium is bigger than the second. (iv) The first Ionisation Energy of Nitrogen is smaller than that of Oxygen.(ai) Mg(g) ----> Mg+(g) + e-
    (aii) Cl(g) + e- ----> Cl-(g)
    (bi) True as they both have an electronic configuration of 1s2.
    (bii) True as Lithium is smaller that sodium so that it is more difficult to lose its electron.
    (biii) False, the second Ionisation Energy is higher as there are less electrons in the ion but the same number of protons so that the pull on the outer electron is greater.
    (biv) False, Nitrogen has a higher Ionisation Energy because it has a half full p-subshell which gives it extra stability and the electron lost from oxygen is paired so that the repulsion of the second electron in the orbital, makes it easier for the electron to be lost
  42. 42(a) Write an equation representing the first Ionisation Energy of Sodium. (b) The first Ionisation energy of Sodium is 496 kJmol-1. In the following list, underline the most likely value for the second Ionisation Energy of Sodium; 296 596 4563(a) Na(g) ----> Na+(g) + e-
    (b) 4563kJmol-1 as there is a large increase given that the second electron is in an inner shell.
  43. 43Which has the larger value; (a) The first Ionisation Energy of Sodium or Magnesium? (b) The first Ionisation Energy of Beryllium or Boron? (c) The first Ionisation Energy of Nitrogen or Oxygen? (d) The first Ionisation Energy of Sodium or Neon? (e) The first Ionisation Energy of Sodium or the second Ionisation Energy of Sodium?(a) First Ionisation Energy of Magnesium
    (b) First Ionisation Energy of Beryllium
    (c) First Ionisation Energy of Nitrogen
    (d) First Ionisation Energy of Neon
    (e) Second Ionisation Energy Of Sodium
  44. 44(a) Write equations to represent the first and second Ionisation Energies of Magnesium. State the units. (b) Explain why; (i) The 1st Ionisation Energy of Magneiums is higher than that of Calcium. (ii) The 3rd Ionisation Energy Of Magnesium is much higher than the 2nd Ionisation Energy. (iii) The 1st Ionisation Energy of Magnesium is slightly larger than that of Aluminium(a) Units kJmol-1
    First Ionisation Energy Of Magnesium:
    Mg(g) ----> Mg+(g) + e-
    Mg+(g) ----> Mg2+ + e-
    (bi) Mg: 1s2, 2s2 2p6, 3s2
    Ca: 1s2, 2s2 2p6, 3s2 3p6 3d0, 4s2
    The Magnesium atom has 1 less shell than that of Calcium so that its outer electron is close to the nucleus and there is less shielding. Therefore, the attraction between the nucleus and the outer electron is larger in Magnesium than in Calcium, even though it has a lower nuclear charge.
    (ii) Mg: 1s2, 2s2 2p6, 3s2
    The third electron is in an inner shell and thus there is a greater attraction to the nucleus due to less shielding and a smaller distance from the nucleus. As a result it is much more difficult to lose this electron.
    (iii) Mg: 1s2, 2s2 2p6, 3s2
    Al: 1s2, 2s2 2p6, 3s2 3p1
    In Magnesium the electron is lost from a full subshell which has extra stability thus making it more difficult for the electron to be lost. Therefore Magnesium has a higher first Ionisation Energy than Aluminium.
  45. 45(a) Write the equations to represent; (i) The first Ionisation Energy of Potassium (ii) The second Electron Affinity of Oxygen (b) From the following list, underline the most likely value for the second Electron Affinity of Oxygen; -560 +800 -800 (c) The following is the list of the first eight ionisation Energies (in kJmol-1) of element X 1000 2260 3390 4540 6990 8490 27100 31700 (i) In which group of the Periodic Table is element X? (ii) Element Y is in the same group of the Periodic Table as element X. Its third ionisation Energy is 2490kJmol-1. Is element Y above or below element X in the Periodic Table?(ai) K(g) ----> K+(g) +e-
    (ii) O-(g) + e- ----> O2-(g)
    (b) +800 kJmol-1 as the second Electron Affinity is endothermic due to the repulsion between the negative ion and the incoming electron being gained.
    (ci) Element X is in Group VI due to the large increase from the sixth to the seventh Ionisation Energy showing that the seventh electron is in an
    inner shell.
    (cii) Element Y is below element X in the Periodic Table as its corresponding Ionisation Energy is lower, showing that the electron is
    further away from the nucleus.
  46. 46Define RadioactivityThis is the spontaneous emission of radiation by an atom whose nucleus is unstable due to an excess of internal energy.
  47. 47Define gamma-emissionThe emission of highly energetic electromagnetic waves with a very short wavelength.
  48. 48Define alpha emissionThe emission of essentially fast moving helium nuclei.
  49. 49Define beta-emissionThe emission of electrons which have been ejected from the nucleus.
  50. 50A radioactive sample emitting all three types of radiation is placed in a lead block. How would a beam of; (i) alpha (ii) beta (iii) gamma behave in the electrical field?(i) Alpha particles are deflected in an electrical field
    (ii) Beta particles are deflected in an electrical field.
    (iii) Gamma particles pass right through the field without being deviated.
  51. 51Explain the term half-life of a radioactive isotope.The half-life of a radioactive substance is the time taken for half of the initial number of radioactive atoms to decay. It is a characteristic property of the isotope.
  52. 52What is the order of the decay reaction?1st order
  53. 53The half-life of Carbon 14 is 5700 years. Living tissue in active contact with the atmosphere has an activity of 15.3 counts per minute per gram of Carbon. A fossil tree gives 3.83 counts per minute per gram of carbon. How old is the fossil tree?Answer
  54. 54The activity of the radioisotope of Sodium decreases to 12.5% of the original value in 72 hours. Find its half-lifeAnswer
  55. 55The half-life of Sodium 24, a beta emitter, is 15.0 hours. A patient receives a dose of sodium chloride, containing Sodium 24 giving a reading of 1200 counts per second in a blood sample. How many hours must pass for the reading of this sample to fall to 75 counts per second?Answer
  56. 56The half-life of Lead-210 is 21 years. How long after the isolation of a sample of this isotope will only 1/8th of the original mass be left?Answer
  57. 57If the activity of Thorium 234 is reduced to 25% in 48 days, what is its half-life?Answer
  58. 58The half-life of Thorium 234 is 24 days. Approximately how long will it take for the activity of a sample to decrease to 3% of its original value?Answer
  59. 59(i) Suggest a medical application for any named isotope of your choice. (ii) Why is the knowledge of the half-life of this isotope essential to its application?(i) Iodine-131 in KI. Used for hyperthyroid and thyroid cancer. The thyroid produces a hormone, thyroxin, which has iodine as part of the molecule. The radioactive iodine will concentrate in the thyroid. The radiation given off will kill the rapidly dividing cells. The half-life of Iodine-131 is
    8.1 days. Beta and gamma rays are given off.
    Gadolinium-153. Used to measure bone demineralization. It gives off gamma and x-rays. It is used to scan the bones and to measure the bone density.
    (ii) The half-life must be short so that the desired effect is obtained and then the level of emitted radiation falls to a safe level in a short time. Knowing the half-life the doctors can determine the time needed for a certain amount of the radioactive substance to emit a safe level of radioactivity so as to cause the least amount of damage.
    The half-life must be known so that the correct amount of radiation is used to get the desired effect. The half-life is long so that the emitted radiation takes a long time to fall to unsatisfactory levels.
  60. 60Define Electron AffinityThe Electron Affinity is the enthalpy change which occurs when gaseous atoms or ions of an element gain electrons to form gaseous negative ions.
  61. 61Define the 1st Electron AffinityThe 1st Electron Affinity is the enthalpy change which occurs when 1 mole of gaseous atoms gain 1 mole of electrons to produce 1 mole of gaseous anions each with a charge of -1
  62. 62Define the 2nd Electron AffinityThe 2nd Electron Affinity is the enthalpy change which occurs when 1 mole of negative ions, each with a charge of -1, gains 1 mole of electrons to produce 1 mole of gaseous anions each with a charge of -2
  63. 63Are values of Electron Affinity exothermic or endothermic? Why?All values of the 1st Electron Affinities are negative (exothermic) and are accompanied by a release of energy. The 2nd electron affinity is endothermic as energy must be supplied to overcome the repulsion between the negative ion and the incoming electron.

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Flashcards on Atomic Structures, created by mysticalfirefox on 15/04/2015.
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