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We are now in a position to discuss the electronic structure of the simplest molecule: H2. For the low-lying electronic states of H2, the BO approximation is completely satisfactory, and so we will be interested in the electronic Hamiltonian. a “B” label the two nuclei.
Revision notes on 2.4.1 Water & the Hydrogen Bond for the CIE A Level Biology syllabus, written by the Biology experts at Save My Exams.
understand why and how atoms form bonds. draw Lewis dot and line structures to represent chemical bonds. What is life? Why is an elephant alive but a table inert? Why are cells alive but their contents when transferred to a flask inanimate?
(C) The electrons determine an atom’s energy and its ability to participate in chemical bonds. 2. (C) Hydrogen bonds form between adjacent water molecules. 3. (D) Oxygen will share two electrons with carbon, and carbon will share two electrons with oxygen, forming a double bond. Oxygen is more electronegative than carbon; therefore, the covalent
The hydrogen and oxygen atoms that combine to form water molecules are bound together by covalent bonds. The electron from the hydrogen atom divides its time between the outer shell of the hydrogen atom and the incomplete outer shell of the oxygen atom.
Based on the concept of electronegativity as we now understand it, we can surmise that the oxygen (O) atom will tend to "pull" the electrons away from the hydrogen (H) when they are interacting.
The typical definition of hydrogen bond (or H-bond) invokes the presence of 3 atoms, generally named as X, H and A. X and A can be different elements, whereas H is always hydrogen. Following this convention, we represent the hydrogen bond with a dotted line, as follows: . X-H∙∙∙A.
