DAT General Chemistry: Atomic Structure and Periodic Trends

Question 1

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

Accepted Answer

18

Answer

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

Question 2

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

Accepted Answer

Sulfur

Answer

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

Question 3

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

Accepted Answer

3p

Answer

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

Question 4

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

Accepted Answer

5.0 × 10⁻⁷ m

Answer

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.

Question 5

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

Angular momentum quantum number (l)

Answer

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

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