General Chemistry: Atomic Structure and Periodic Trends Flashcards

What is the maximum number of electrons that can occupy the third principal energy level (n = 3)?

Answer: 18

The maximum number of electrons in principal energy level n is given by 2n², so for n = 3: 2(3²) = 18 electrons.

Which element has the ground-state electron configuration [Ne]3s²3p⁴?

Answer: Sulfur

[Ne]3s²3p⁴ represents 16 total electrons (10 from Ne core + 6 valence), which corresponds to sulfur (Z = 16).

According to the Aufbau principle, which subshell is filled immediately before the 4s subshell?

Answer: 3p

The Aufbau filling order proceeds as 1s, 2s, 2p, 3s, 3p, 4s — so 3p fills directly before 4s.

What is the wavelength of light with a frequency of 6.0 × 10¹⁴ Hz? (c = 3.0 × 10⁸ m/s)

Answer: 5.0 × 10⁻⁷ m

Using λ = c/f: (3.0 × 10⁸ m/s) ÷ (6.0 × 10¹⁴ Hz) = 5.0 × 10⁻⁷ m, which falls in the visible light range.

Which quantum number determines the shape of an atomic orbital?

Answer: Angular momentum quantum number (l)

The angular momentum quantum number (l) defines orbital shape: l = 0 (s), l = 1 (p), l = 2 (d), l = 3 (f).

Iron has atomic number 26. In which period and group of the periodic table does it appear?

Answer: Group 8, Period 4

Iron (Z = 26) has configuration [Ar]3d⁶4s², placing it in Period 4 and Group 8 as a d-block (transition) element.

Which of the following Period 3 elements has the largest atomic radius?

Answer: Na

Atomic radius decreases across a period due to increasing nuclear charge, so Na (leftmost of the group) has the largest atomic radius.