Orbital Valency

The interaction of two atoms, each with one $2p$ electron, is studied by a method similar to that used by Kemble and Zener. An atomic wave function whose radial part is of the form const. re^-kr/2 (that is, with no nodes) is used. Complete potential energy curves are obtained for the twelve possible states, which are ¹Δg, ³Δᵤ, ¹Πg, ¹Πᵤ, ³Πg, ³Πᵤ, ¹Σᵤ^-, ³Σg^-, two ¹Σg⁺, and two ³Σᵤ⁺. The most stable states are ³Σᵤ⁺ (lowest) and ¹Σg⁺, which arise from m_lᵃ=0 and m_lᵇ=0, and in which there is the maximum overlapping of charge. The states with least overlapping of charge are those where m_lᵃ=±1 and m_lᵇ=±1, resulting in ¹Δg, ³Δᵤ, ¹Σg⁺, ¹Σᵤ^-, ³Σg^-, ³Σᵤ⁺, which are all repulsive. The II states lie in between, and are attractive. The present work gives precision to the ideas of Heitler on orbital valency, yields a positive exchange energy integral for the lowest states, and may be taken as supporting the conceptions of Slater about directed valency.