Consideration is given to two charge-shift bonding schemes for a symmetrical 4-electron 3-centre hyperbonding unit with three overlapping atomic orbitals. One of these schemes includes the other scheme and the Hach-Rundle-Pimentel 3-centre molecular orbital model as special cases. SF4 and [Cu (H2O)(6)](2+) are used to illustrate aspects of charge-shift bonding and recoupled-pair bonding theory by generating the increased-valence structures that are associated with the preferred scheme. (C) 2016 Elsevier B.V. All rights reserved.