Potassium (K)

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Practice potassium

Questions from the course about potassium. If you’re signed in, your answers count toward your progress.

1. Question 1Photoelectric effect: kinetic energy of ejected electronsChallenging

   Light of wavelength $327\ \mathrm{nm}$ shines on a clean potassium surface. The work function of potassium is $\phi = 2.29\ \mathrm{eV}$ ($1\ \mathrm{eV} = 1.602 \times 10^{-19}\ \mathrm{J}$). What is the maximum speed of the ejected electrons, in $\mathrm{m\,s^{-1}}$? ($m_e = 9.109 \times 10^{-31}\ \mathrm{kg}$)

   Your answer (in the unit shown)

   $\mathrm{m\,s^{-1}}$

   Scientific notation: type 4.86e-7 or 4.86 x 10^-7.

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2. Question 2Ground-state electron configurationWarm-up

   Which is the ground-state electron configuration of a neutral potassium atom ($\ce{K}$)?

   A$[\mathrm{Kr}]\,4s^{1}$B$[\mathrm{Ar}]\,3d^{1}$C$[\mathrm{Ar}]\,4s^{2}$D$[\mathrm{Ar}]\,4s^{1}$

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3. Question 3Electron configuration of an ionWarm-up

   Which is the ground-state electron configuration of $\ce{K+}$?

   A$1s^{2}\,2s^{2}\,2p^{6}\,3s^{2}\,3p^{6}$B$1s^{2}\,2s^{2}\,2p^{6}\,3s^{2}\,3p^{6}\,4s^{1}$C$1s^{2}\,2s^{2}\,2p^{6}\,3s^{2}\,3p^{6}\,4s^{2}$D$1s^{2}\,2s^{2}\,2p^{6}\,3s^{2}\,3p^{5}\,4s^{1}$

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