Honors Chemistry

Chapter 4 Problem Set #3 Key

 

1.      Electromagnetic radiation is fluctuating electric and magnetic fields.  It has wave and particle properties.  Each type of EMR (radio waves, visible light, x-rays, etc.) varies from other types in their frequency, wavelength and energy per photon.

 

2.      W=c/F = (3.00 x 108  m/s)   /  (4.78 x 1014  s-1)  =  6.28 x 10-7  m

 

3.      Two things. Energy comes in packets or bundles called quanta, and the energy of an electron when it is around an atom can only be certain specific values and no others.

4.      If a photon of light with an energy equal to the difference between the ground state and some higher energy level hits the atom, the electron can take on that energy and be “promoted” to that higher energy level.  If we know all of the photons that are absorbed by an atom, then we know all of the “differences” between the ground state and the other energy levels.  If we also know how much energy is required to remove an electron completely from the atom, then we know the ground state.  We would then know all of the energy levels that atom could have.  This tells us how electrons are arranged around an atom.

5.      An electron could go from the 3rd energy level to the ground state, or from the 3rd to the 2nd energy level, and once in the 2nd would move to the ground state.  Each of these changes would result in a different size photon being released from the atom.

6.       

 

Energy

Frequency

Wavelength

Color

5-3

1.55 x 10-19   J

2.34 x 1014    s-1

1.28 x 10-6    m

Infra red

5-2

   4.57 x 10-19   J

6.90 x 1014    s-1

4.35 x 10-7    m

Violet

5-1

2.093 x 10-18   J

3.159 x 1015  s-1

9.50 x 10-8    m

Ultra violet

 

7.      p orbitals are present in all energy levels except the first. d orbitals are present in energy levels above the 3rd level.  f orbitals are present above the 5th level.

8.      The number of TYPES of orbitals is the same as the principle quantum number.

9.      The information you need to give in a description of a set of orbitals should include the number of orbitals involved, the name for each, the shape and orientation (to the nucleus and each other) and the number of electrons associated with each.  There would be three orbitals in the set of p orbitals in the second energy level of a neutral fluorine atom, called the 2px, 2py, and 2pz orbitals.  Each orbital would be composed of two regions in space, on either side of the nucleus, each shaped like the top of a hamburger bun.  The three p orbitals would be at right angles to each other, aligned with the x-axis, y-axis and z-axis. Two of these orbitals would have two electrons associated with them, and the third would have one electron.

10.  Lithium has 1 valence electron, sodium has 1, and potassium has 1. (Note their arrangement in the periodic table!)

11.  Fluorine has 7 valence electrons, chlorine has 7 and bromine has 17.

12.  Scandium is the first element to begin filling d orbitals. Lanthanum is the first to start filling f orbitals.

13.  Indium through xenon are in the process of filling p orbitals in their valence shell.

14.  Al  1s2  2s22px2py2pz2  3s23px1                  Ca   1s2  2s22px2py2pz2   3s23px2py2pz2   4s2  

      Cl  1s2  2s22px2py2pz2   3s23px2py2pz1        C    1s2  2s22px1py1 

15.  Can’t show the dots with MSWord, so I’ll describe them: All Lewis or electron dot diagrams have the symbol of the element with single dots or pairs of dots (or no dots) above, below, left or right of the symbol.

Sulfur – An S with a pair of dots on 2 sides and a single dot on 2 sides (Total of 6 dots)

Fluorine – An F with a pair of dots on three sides and a single dot on the remaining side

            Nitrogen – An N with a pair of dots on one side and single dots on the remaining 3 sides

            Silicon – Si with a single dot on each of the 4 sides.

            Selenium – Se with a pair of dots on two sides and single dot on 2 sides (just like Sulfur?)

16.   15.00 moles of nitrogen molecules will require 45.00 moles of hydrogen molecules and make 30.00 moles of ammonia molecules

17.  a. 5.220 moles (molar mass = 22.990 g/mol)   b. 1.305 moles   c. 2.610 moles   d. 161.8 g (molar mass = 61.979 g/mol)

18.  a. 0.00254 mol (molar mass = 44.0962 g/mol)   b. 0.0127 mol   

      c. 0.335 g  of carbon dioxide (molar mass = 44.009 g/mol) and 0.183 g of water (molar mass = 18.0149 g/mol)