AP Atomic Structure and Periodicity 2

Question 1

An electron in a hydrogen atom transitions from n = 4 to n = 2. What is the wavelength of the emitted photon? (RH = 2.179 × 10⁻¹⁸ J, h = 6.626 × 10⁻³⁴ J·s, c = 3.00 × 10⁸ m/s)

Accepted Answer

486 nm

Answer

656 nm

Answer

410 nm

Answer

434 nm

Question 2

Which set of quantum numbers is NOT allowed for an electron in an atom?

Accepted Answer

n=3, l=3, ml=+2, ms=+½

Answer

n=3, l=2, ml=+2, ms=+½

Answer

n=2, l=1, ml=−1, ms=−½

Answer

n=4, l=0, ml=0, ms=+½

Question 3

The first ionization energies (in kJ/mol) for elements in Period 3 include an unusually high value for Mg (738) compared to Al (577). What best explains why Al has a lower first ionization energy than Mg?

Accepted Answer

Al's outer electron is in a 3p orbital, which is higher in energy and better shielded than Mg's 3s electron

Answer

Al has a larger atomic radius than Mg

Answer

Al has more electrons, increasing electron-electron repulsion

Answer

Mg has a higher nuclear charge that attracts electrons more strongly

Question 4

Which of the following correctly lists the ions in order of increasing radius: Na⁺, Mg²⁺, Al³⁺, O²⁻, F⁻?

Accepted Answer

Al³⁺ < Mg²⁺ < Na⁺ < F⁻ < O²⁻

Answer

O²⁻ < F⁻ < Na⁺ < Mg²⁺ < Al³⁺

Answer

Na⁺ < Mg²⁺ < Al³⁺ < F⁻ < O²⁻

Answer

F⁻ < O²⁻ < Na⁺ < Mg²⁺ < Al³⁺

Question 5

What is the de Broglie wavelength of an electron (mass = 9.11 × 10⁻³¹ kg) moving at 2.00 × 10⁶ m/s? (h = 6.626 × 10⁻³⁴ J·s)

Accepted Answer

3.64 × 10⁻¹⁰ m

Answer

7.28 × 10⁻¹⁰ m

Answer

1.82 × 10⁻¹⁰ m

Answer

3.64 × 10⁻⁷ m

Question 6

An element has the electron configuration [Kr]4d¹⁰5s²5p⁴. What is the element, and how many unpaired electrons does it have?

Accepted Answer

Tellurium (Te), 2 unpaired electrons

Answer

Selenium (Se), 2 unpaired electrons

Answer

Tellurium (Te), 4 unpaired electrons

Answer

Tin (Sn), 0 unpaired electrons