Niobium is the current material of choice for superconducting radiofrequency (SRF) cavities in particle accelerators. Nb found its ubiquitous use and extensive study in SRF cavities due to both its normal and superconducting state properties. Experimental and theoretical studies have documented and studied mechanisms in which even local hot spots from inhomogeneities, defects, and topographical variations can heat and quench entire SRF cavities. Thus, optimal preparation of Nb SRF cavity surfaces are required to prepare energetically efficient SRF cavities and keep costs of operation from being prohibitively high. In other words, the relationship between atomic-scale surface structure and the resulting superconducting properties at the surface is critical in improving and developing next generation SRF cavity materials. While well-studied, the formation and evolution of surface defects and compositional inhomogeneities remains a challenging part of SRF cavity treatment design and implementation. Such an understanding of the role of surface structure and chemical composition as well as their resulting effects on superconductivity at the surface remains elusive. This thesis seeks to make a start to this foundational understanding with in situ high temperature measurement of atomic scale surface structure, vibrational dynamics, and surface EPC on the metallic Nb(100) surface and its surface oxide reconstruction (3x1)-O/Nb(100). These measurements begin with the discovery of the (3x1)-O/Nb(100)’s high temperature stability and structural/ compositional persistence under SRF cavity preparation conditions. Then, a key driving force for the unusual stability of the (3x1)-O/Nb(100) was elucidated with inelastic HAS TOF measurements and ab initio density-functional theory (DFT) calculations, revealing abnormally strong Nb-O and Nb-Nb bonds that make up the characteristic ladder 10 structure. This means the ladder crests of the (3x1)-O/Nb(100) not only introduces new, relatively strong Nb-O interactions, but it significantly strengthens the Nb-Nb interactions. In this way the (3x1)-O/Nb(100) passivates and stabilizes the surface. These results demonstrate the significant role niobium oxides play in the optimization of growth strategies and coating procedures for next–generation SRF materials. Next the atomic-scale structure’s effect on the superconductivity was investigated using HAS’s sensitivity to EPC. HAS simultaneously measured the surface electron-phonon coupling (EPC, SEPC) constant (, ) and in situ high temperature atomic-scale surface structure of the unreconstructed, metallic Nb(100) surface as well as the (3x1)-O/Nb(100) oxide reconstruction. Ab initio DFT with local averaging agrees well with the HAS data. Furthermore, some variations in subsurface C and O and their effect on the SEPC are discussed. The Nb(100) surface is 0.50 ± 0.08 while that of the (3x1)-O/Nb(100) surface oxide reconstruction is is 0.20 ± 0.06. The measured for the Nb(100) surface is ~1/2 the reported bulk Nb values. The significance of Nb(100)’s diminished EPC was elucidated by estimating relevant superconducting properties from the measured , surface Debye temperature, known material parameters, and well-established equations. These results indicate that the Nb(100) surface has decreased superconducting properties relative to the bulk. This study shows that these effects may be due also to the interface itself even without oxygen. Additionally, the λ S measured for the (3×1)-O surface reconstruction is further diminished from the metallic, unreconstructed Nb(100) value and the reported bulk Nb λ values. Furthermore, varying subsurface O has no significant effect on the λ S of the (3×1)-O reconstruction. While the metallic, unreconstructed Nb(100) surface is significantly affected by accumulated subsurface C and O, the (3×1)-O reconstruction stabilizes its λ S against the effects of subsurface O. These results contain the first measured for the metallic 11 Nb(100), (3x1)-O/Nb(100), and any Nb surface. These measurements begin a fundamental understanding of atomic-scale surface structure’s effect on EPC and superconductivity in Nb.