Chemistry Review (Chapter 7-9)

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Chemistry Review (Chapter 7-9)
2009-11-20 21:03:55

Chemistry Review for Exam 3 Chapter 7-9
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  1. How are Cathode rays formed?

    Cathode rays are formed when electricity passes through gases at very low pressures.
  2. What does Thomson's extensive studies of cathode rays proved?
    Thomson's extensive studies of cathode rays proved taht they are negatively charged fundamental particles (which are now called electrons) found in all matter.
  3. What did the Experiments of Thomson also established besides that cathode rays are found in all matter?

    Thomson also established the mass-to-charge ratio of electrons by observing their deflections in electric and magnetic fields.

  4. Who established the charge on an electron? How?

    The charge on an electron was established by Millikan in a study of behavior of electrically charged oil droplets in an electric field.

  5. What does an electron bears?
    An electron bears one fundamental unit of negative electric charge.
  6. What did Thomson's raisin pudding model showed us?
    Thomson's raisin pudding model viewed an atom as electrons ("raisins") embedded in a positively charged "pudding."
  7. What is Rutherford's interpretation of alpha particles?
    Rutherford's interpretation of the scattering of alpha particles by metal foils suggested that the atom had a tiny, massive, positively charged nucleus that is surrounded by electrons.
  8. What did later experiments by Rutherford and others confirmed?
    Later experiments by Rutherford and others confirmed his atomic model and showed that the nucleus consists of protons and neutrons, which account for practically all the mass of an atom.
  9. What is mass spectrometry is used to establish? And what is it?

    Weighted atomic masses of the elements and relative abundances of the isotopes of an element can be established by mass spectrometry, a technique that seperates charged particles according to their mass-to-charge ratios.
  10. What is electromagnetic radiation?
    Electromagnetic radiation is an energry transmission in the form of oscillating electric and magnetic fields.
  11. What does oscillations produes?
    Oscillations produces electromagnetic waves that are characterized by their frequencies, wavelengths and velocity.
  12. What is the electromagnetic spectrum?

    The complete span of possibilities for frequency and wavelength is described as the electromagnetic spectrum, of which visible light is only a very small part.

  13. What is continuous spectrum?
    Light consisting of essentially all wavelength components in a region of the electromagnetic spectrum is a continuous spectrum (for example, the rainbow of colors obtained when a beam of sunlight is dispersed by a glass prism or raindrops in the sky).
  14. What does energetically excited gaseous atoms do?
    Energetically excited gaseous atoms typically emit an emission spectrum containing only a discrete set of wavelength components in the form of a line spectrum.
  15. What did Planck explained?
    Planck explained the spectral characteristics of black-body radiation by proposing that the energy of electromagnetic radiation is limited to intergral multiples of fundamental quantify that is called a quantum and has the value E=hv where h is defined as Planck's constant.
  16. What is the photoelectric effect?
    The photoelectric effect is the emission of electrons by illuminated surfaces. This is explained by thinking of quanta of energy as concentrated into particles of light called photons.
  17. Explain Bohr's theory.
    Bohr's theory requires the electron in a hydrogen atom to be in one of a discrete set of energy levels. The fall of an electron from an excited state to a ground state releases a discrete amount of energy as a photon of light with a characteristic frequency. Bohr's theory accounts for the observed atomic spectrum of hydrogen and is also applicable to the spectra of other one-electron species, such as He+ and Li2+.
  18. What is a more satisfactory quantum mechanical treatment of atomic structure? And what does it do?
    A more satisfactory quantum mechanical treatment of atmoic structure is based on two additional fundamental concepts. These concepts are the wavelike properties of small particles and the Heisenberg uncertainty princeiple. These concepts transform the precisely described Bohr atom into an atomic model that replaces certainty with probability. Specifically, De Broglie proposed that a particle of mass moving at speed will have a wavelength. Thus, the electron in a hydrogen atom can be viewed as a matter wave enveloping the nucleus.
  19. What is quantum mechanics?
    The representation of the wavelike properties of the electron through a wave equation is called quantum mechanics, and solutions of the wave equation are wave functions.
  20. What does wave functions require?
    Wave functions require the assignment of three quantum numbers: the principal quantum number, n, the orbital angular momentum quantum number, l, and the magnetic quantum number ml.
  21. What are atomic orbitals?
    Atomic orbitals are wave functions with acceptable values of the three quantum numbers.
  22. What does Orbitals describe?
    Orbitals describe regions in an atom that have a high probability of containing an electron or a high electronic charge density. Orbitals having the same value of n are in the same principal engery level, or principal shell. Those with the same value of n and of l are in the same subshell. The shapes associated with orbitals depend on the value of l. an s orbital (l = 0) is spherical, and a p orbital (l =1) is dumbbell-shaped.
  23. What does n, l, and ml quantum numbers define?
    They define an orbital, but a fourth quantum number is also required to characterize an electron in an orbital. The fourth quantum number is the electron spin quantum number, ms. This quantum number may have either of two values: +(1/2) or -(1/2).
  24. Explain the wave mechanical treatment of the hydrogen atom.
    The wave mechanical treatment of the hydrogen atom can be extended to multielectron atoms, but with two essential differences: (1) Energy levels are lower in multielectron atoms than in the hydrogen atom, and (2) the energy levels in multielectron atoms are split; that is, the different subshells of a principal shell have different energies. The order of increasing subshell energy in a principal shell is s<p<d<f. All the orbitals within a subshell, however, have the same energy (they are degenerated orbitals).
  25. What is an electron configuration?
    Electron configuration is the distribution of electrons in orbitals among the subshells and principal shells in an atom. Three types of notation of electron configuration are the spdf notation, the noble-gas-core abbreviated notation, and the orbital diagram.
  26. What are the rules for electron configurations?
    To write a probable electron configuration, we note that (a) electrons tend to occupy the lowest-energy orbitals available, (b) no two electrons can have all four quantum numbers alike (Pauli exclusion principle), and (c) where possible, electrons occupy orbitals singly and with parallel spins, rather than in pairs (Hund's rule).
  27. What is the Aufbau Principle?
    The aufbau principle describes a process of hypothetically building up one atom from the atom having the preceding atomic number. With this principle and the other ideas cited in the chapter, it is possile to predict probable electron configurations for many of the elements. In the aufbau process for the main-group elements, electrons ar eadded to either the s or the p subshell of the principal shell of highest principal quantum number (n). In transistion elements, electrons go into the d subshell that is one shell in fromt he outermost occupied principal shell.
  28. Explain Periodic Relationships.

    Elements with similar electron configurations fall in the same group of teh periodic table. For main-group elements, the group number correspons to the number of electrons in the principal shell of highest quantum number. The period number is the same as the principal quantum number of the valence shell. the division of the periodic talbe into s-, p-, d-, and f-blocks assists in the assignment of probable electron configureations. With in the f-block, the lanthanide series consists of elements in which the 4f subshell is the one being filled; the actinide series consists of elements in which the 5f subshell is being filled.

  29. What are Valence electrons?
    Valence electrons occupy the outermost occupied principal shell and have the highest principal quantum number of the electrons within the atom or ion.
  30. What are Core electrons?
    Core electrons occupy the inner shells, those with principal quantum numbers less than that of the valence shell.
  31. What is the difference between paramagnetic and diamagnetic?
    An atom with all electrons paired is diamagnetic, and an atom with one or more unpaired electrons is paramagnetic.
  32. What does the periodic law describe?
    The periodic law describes the regular reccurrence of certain physical and chemical properties of atoms when they are arranged by increasing atomic number. Clear trends are seen in plots of atomic radius versus atomic number.
  33. What does the specific definition of radius dimensions depends on?
    The specific definition of radius dimensions depends on the bonding environment in which elements are found; in molecules, we speak of the covalent radius of the atoms, and in metals, we speak of the metallic radius of the atoms. For ionic species, the size is expressed in terms of the ionic radius. Various species can be isoelectronic (contain the same number of electrons) but still have different atomic or ionic radii because the effective nuclear charge is different in each.
  34. Define effective nuclear charge.

    The effective nuclear charge (Zeff) felt by an outer electron in an atom is the actual nuclear charge less the screening effect of all other electrons in the atom.
  35. Define Ionization energy.

    Ionization energy is the energy required to remove an electron from a ground-state atom (or ion) in the gaseous state.
  36. Define Electron affinity.
    Electron affinity is the energy change associated with the addition of an electron to a gaseous atom or ion.
  37. What are the regions of the periodic table designated to? And what is it related to?
    The regions of the periodic table is designated to metals, nonmetals, metalloids, and the noble gases. This is related to the values of atomic properties. In general, matallic properties are associated with the ease with which atoms lose electrons; and nonmetallic properties, with the ease with which they gain electrons. The most metallic elements are located towards the left and bottom of the periodic table, and the most nonmetallic elements are located towards the right and top of the table.
  38. Using atomic properties and the periodic table, explain the behavior of the elements.
    The colors produced from metal flame test, oxidation and reduction properties, and the acid-base behavior of oxides all exhibit trends consistent with the periodic law. For example, oxides of nonmetals are generally acidic oxides; that is, they produce an acid upon reaction with water. Basic oxides, oxides that react with water to form bases, are generally oxides of metals. Oxides of elements having both metallic and nonmetallic character are amphoteric; they can react with either an acid or a base.
  39. Explain what are chemical bonds.
    Chemical bonds form when the attractive forces between engatively charged electrons and positively charged nuclei exceed the repulsions between the nuclei to the maxiimum extent possible. The nature of the chemical bonds in a material determines many of its properties.
  40. What is a Lewis symbol?
    A Lewis symbol represents the valence electrons of an element, shown through dots distributed about the chemical symbol of the element. Lewis symbols of main-group elements are related to their locations in the periodic table. In forming compounds, main-group elements generally tend to follow an octet rule, which states that bonded atoms tend to acquire electron configurations having eight electrons in the valence shell.
  41. How does an ionic bond form?
    An ionic bond forms through the transfer of electrons from metal to nonmetal atoms and the subsequent electrostatic attraction between the resulting ions.
  42. What does an ionic crystal consists of?
    An ionic crystal consists of an extended regular arrangement of ions.
  43. How can the ionic bonds between nonmetals and s-block, p-block, and a few d-block metals be represented?
    The ionic bonds between nonmetals and s-block, p-block, and a few d-block metals can be represented through the Lewis symbols of respective anions and cations. this representation indicates the nature of electron transfer and the basis for electrostatic attration.
  44. What is lattice energy?
    The net energy decrease in the formation of an ionic crystal from its gaseous ions is the lattice energy. A Born-Haber cycle relates the lattice energy and enthalpy of formation of an ionic compound, together with other atomic and molecular properties.
  45. When does a covalent bond forms?
    A covalent bond forms when two atoms share electrons.
  46. What is a Lewis structure show?

    A Lewis structure of a molecule show sthe arrangement of atoms in the molecule and covalent bonds between them. The lewis structure depicts electron pairs in the molecule as either bonding pairs or lone pairs. Usually, each atom in a Lewis structure acquires a noble-gas electron configuration, which for most atoms is a valence-shell octet of electrons.
  47. What is the difference between a single bond, a double bond, and a triple bond?
    A convalent bond involving one electron pair is called a single bond. A double bond involves two shared electron pairs, and a triple bond involves three.
  48. Define electronegativity.

    Electronegativity (EN) is a measure of the ability of an atom to attract the electrons of a chemical bond to itself and is related to the position of an element in the periodic table. In a convalent bond between atoms of different EN values, electrons are displaced towards the atom with the higher EN. Chemical bonds vary from nonpolar covalent (zero or very small ∆EN) to polar covalent to ionic (large ∆EN).
  49. What are the strategy for writing Lewis structures?

    Writing plausible Lewis strutures for molecules or polyatomic ions involves two general tasks: (1) writing the skeletal structure, which consists of one or more central atoms bonded to a number of terminal atoms, and (2) distributing the valence electrons among the atoms so as to (usually) follow the octet rule Resonance describes a phenomenon in which two or more Lewis structures have the same skeletal structure but different distributions of electrons among the bonded atoms. The best description of the actual structure, the resonance hybrid, is a combination of plausible resonance structures. In a resonance hybrid, some of the bonding electrons are delocalized over serval atoms. The resonance hybrid should conform to experimental data, such as bond lengths and/or bond energies, if these data are available.
  50. What are the exception to the octet rule?
    Exceptions to the octet rule are found in odd-electron molecules and in molecular fragments calle dfree radicals. A few structures appear to have too few electrons to complete the octets of all atoms in the molecule or ion. Some structures appear to have too many. In the latter case, a central atom may have an expanded valence shell involving five, six, or even more elctron pairs.
  51. What is bond length?
    Bond length, which in some cases can be related to atomic radii, is the internuclear distance between two bonded atoms. Bond length is greatly affected by bond order, that is, whether the bond is single, double, or triple.
  52. What is Bond-dissociation energy?
    Bond-dissociation energy is the energy required to break one mole of bonds in a gaseous species; its value depends on (1) the atoms in the bond, (2) the bond order, and (3) the particular molecule in which the bond is found. tabulated values are often averaged over a number of molecules containing the same bond. Bond-dissociation energies and average bond energies can be used to estimate enthalpy changes of reactions via the relationship ∆H = ∆Hbonds broken + ∆Hbonds formed.
  53. What are alkenes and Alkynes?
    Unsaturated hydrocarbons have one or more multiple bonds between carbon atoms. Alkenes have double bonds, and alkynes have triple bonds. A characteristic reaction of alkenes and alkynes is their ability to add atoms across the multiple bonds, thereby converting the multiple bonds to single bonds.
  54. Explain the difference between monomers and polymers.

    Some molecules containing multiple bonds undergo polymerization, a reaction in which small molecules (monomers) join together in large numbers to produce a gigantic molecule (polymer). Polymers typically are made up of long carbon chains, have high molecular massess, and often are represented through the structure of only the repeating unit.
  55. Explain the trends of Atomic Radius.

    Atomic Radius increases as the group decreases and the period increases in the periodic table.

  56. Explain the trends of Ionic Radius.
    Ionic Radius increases as the group decreases and the period increases in the periodic table.
  57. Explain the trends of Electron Affinity.
    Electron Affinity increases as the group increases and the period decreases in the periodic table.
  58. Explain the trends of Ionization Energy.
    Ionization Energy increases as the group increases and the period decreases in the periodic table.
  59. Explain the trends of Electronegativity.
    Electronegativity increases as the group increases and the period decreases in the periodic table.