Atomic Structure and Periodicity

Transcription

1 Atomic Structure and Periodicity Atoms and isotopes: Isotopes-#p + same for all but mass number is different b/c of # n o Average atomic mass is weighted average of all the isotopes for an element Average atomic mass will be closest to mass of most abundant isotope Know how the four quantum numbers apply to electron configuration and orbital notation energy associated with an electron (basically the energy level) shape of the orbital s, p, d, f orientation about the x, y, z axes spin of the electron as it moves throughout the atom Electron configuration describes location of the electron using first two quantum #s Orbital notation adds the next two quantum #s and illustrates Hund s Rule Isoelectronic same electron configuration Paramagnetic magnetic when in the presence of a magnet (caused by unpaired electrons) (colored ions) Diamagnetic never magnetic (all electrons are paired) Electron configuration indicates the ground state of an electron. Excited state electron absorbs energy and jumps to a higher energy level; emits energy in the form of light When it returns to its ground state; light emitted is of a certain frequency thus different colors (bright lines) Lowest frequency of visible light is red; highest is violet Relationship between energy, frequency, wavelength: low frequency/low energy/ long wavelength; high frequency/ high energy/ short wavelength Relationship between wavelength and frequency c = Where c = speed of light 3 x 10 8 m/sec, = wavelength in nanometers, = frequency in hertz (sec -1 ) The energy of an electron can be calculated using E = h Where E = energy in Joules, h = Planck s constant = x Jsec, = frequency in hertz PES look at the diagram; determine how many electrons are represented to identify the element; write the electron configuration for that element to match energies to the orbitals represented Mass spectrometry disproves Dalton s theory and proves existence of isotopes including their abundance Properties Atomic Radius size of atom Ionic Radius size of ion Ionization Energy energy required to remove an electron Electronegativity attraction for an electron Must know! Trends and the reason for the trend. Down a group Explanation: more energy levels contain electrons; inner electrons shield the attractive force between p + and e - Across a period Explanation: increasing effective nuclear charge; stronger Z eff can pull on electrons Be able to compare sizes of atoms and ions using atomic structure criteria

2 Multiple Choice 1. The formation of an aluminum ion occurs when 3 electrons are removed. Which electron would require the most energy to remove? A) 3s because it is filled before 3p B) 3p because it is farther from the nucleus C) 3p because it only has 1 electron in the orbital D) 3s because it experiences higher attractive forces 2. Glass for electronic devices needs to be more durable than typical window glass. Sodium ions on the glass surface are replaced by larger ions when the glass is dipped into a molten salt. Which type of salt would give the toughest glass? A) lithium B) magnesium C) potassium D) calcium 3. Which is a list of elements in order of increasing first ionization energy? A) Cl, P, Si B) N, P, As C) Sr, Ca, Mg D) F, Ne, Na 4. Which gives a list of species that are isoelectronic? A) Mg 2+, Ca 2+, Sr 2+ B) F -, S 2-, As 3- C) Fe, Co, Ni D) S 2-, Cl -, K + 5. The electron configuration of atoms of germanium, Ge, is shown below: [Ar core] 3d 10 4s 2 4p 2 This element is known to form more than one oxide. Which pair of formulas includes the two most likely formulas for these oxides? A) GeO and GeO 2 B) Ge O 2 and Ge 2O 7 C) Ge 2O 3 and GeO 2 D) GeO and Ge 2O 3 6. The value of Planck s constant is 6.63 x J sec. The speed of light is 3.0 x 10 8 m sec -1. Which value is closest to the wave length in nanometers of a quantum of light with frequency of 6 x sec -1? A) 10 B) 25 C) 50 D) Which list includes only atoms that are larger than the most common ion of that atom? A) Ca, Cl, P B) Mg, Na, Sn C) Cl, P, N D) Sb, Se, Sr

3 8. Using the PES diagram above, what element is represented? A) Aluminum B) Carbon C) Boron D) Not enough information to determine 9. Where is the 0.77 ev electron located? A) 3s B) 3d C) 4s D) 4d 10. This is a simple mass spectrum showing the relative abundance for seven isotopes of an element. The average atomic mass should be closest to A) 94 B) 95 C) 97 D) 99

4 Free Response Questions 1. Suppose that a stable element with atomic number 119, symbol Q, has been discovered. a) Write the ground-state electron configuration for Q, showing only the valence-shell electrons. b) Would Q be a metal or a nonmetal? Explain in terms of electron configuration. c) On the basis of periodic trends, would Q have the largest atomic radius in its group or would it have the smallest? Explain in terms of electronic structure. d) What would be the most likely charge of the Q ion in stable ionic compounds? e) Write a balanced equation that would represent the reaction of Q with water. f) Assume that Q reacts to form a carbonate compound. 2- i. Write the formula for the compound formed between Q and the carbonate ion, CO 3. ii. Predict whether or not the compound would be soluble in water. Explain your reasoning. 2. Explain each of the following observations using principles of atomic structure and/or bonding. a) Potassium has a lower first ionization energy than lithium b) The ionic radius of N 3- is larger than that of O 2-. c) A calcium atom is larger than a zinc atom. d) Boron has a lower first ionization energy than beryllium.

5 3. In the upper atmosphere, ozone molecules decompose as they absorb ultraviolet (UV) radiation, as shown by the equation below. Ozone serves to block harmful ultraviolet radiation that comes from the Sun. O 3 (g) O 2 (g) + O (g) A molecule of O 3 (g) absorbs a photon with a frequency of 1.00 x s -1. a) How much energy, in joules, does the O 3 (g) molecule absorb per photon? b) The minimum energy needed to break an oxygen-oxygen bond in ozone is 387 kj mol -1. Does a photon with a frequency of 1.00 x s -1 have enough energy to break this bond? Support your answer with a calculation.