Which gas-phase atom in its ground state could have an electron with the quantum numbers n=3, l=2, m₁ = 0, m_u = -1/2 ?

 Gas-phase atom in its ground state could have an electron with the quantum numbers: $n=3$, $l=2, m_l=0, m_u=-\frac{1}{2}$ is $Ti$.

The atomic structure of tungsten has 74 protons and 74 electrons, making it a chemical element with atomic number 74. W represents tungsten in chemical notation. Tungsten Oxidation States and Electron Configuration Tungsten has a [Xe] $4f^{14} 5d^4 6s^2$ electron configuration.

Hence, option D is correct.