Free response · Unit 1 Beta

Photoelectron spectra of sodium and magnesium

Short free response · 4 points

The question

Name: ______________________   Date: ____________   Photoelectron spectra of sodium and magnesium (4 points)

Graph

Photoelectron spectra of Na and Mg

The photoelectron spectra of gaseous sodium atoms and magnesium atoms. Numbers above the peaks are binding energies in MJ/mol; peak heights are proportional to the number of electrons.

Sodium1046.843.670.4963001003010310.3Magnesium1269.075.310.7383001003010310.3Binding energy (MJ/mol), stretched scale, decreasing to the right

  1. (a) Identify the subshell responsible for the peak at 0.738 MJ/mol in the spectrum of magnesium, and state how many electrons it represents. [1 point]

  2. (b) The 1s peak of magnesium is at a higher binding energy than the 1s peak of sodium. Explain why, in terms of Coulomb's law. [1 point]

  3. (c) Aluminum has 13 electrons. Describe how its spectrum would differ from that of magnesium: state where any new peak would appear and its relative height. [1 point]

  4. (d) The first ionization energy of aluminum is lower than that of magnesium. Explain why, using the electron configurations of both atoms. [1 point]