Hydrogen Bonding 8.4 Water (Prelim) 8.4.2 The wide distribution and importance of water on Earth is a consequence of its molecular structure and hydrogen bonding
Syllabus Points Stage 6 preliminary unit on Water. describe hydrogen bonding between molecules plan and perform an investigation to identify and describe the effect of anti-freeze or salt on the boiling point of water
What is a Hydrogen Bond? Hydrogen bonds are the attractive force between the hydrogen attached to an electronegative atom of one molecule and an electronegative atom of a different molecule. Hydrogen (H) needs to be attached to a highly electronegative Oxygen (O), Fluoride (F), Nitrogen (N) atom.
Why are O, F & N so attractive?? In each of these molecules note: 1. A hydrogen atom! 2. the hydrogen is attached directly to one of the most electronegative elements, causing the hydrogen to acquire a significant amount of positive charge. 3. Each of the elements to which the hydrogen is attached is not only significantly negative, but also has at least one "active" lone pair. In these interactions, a hydrogen atom is the donor, and the respective electronegative atom is the acceptor of the bond. Electronegativity Values F (4.0) O (3.5) N(3.0)
Hydrogen Bonding in Water Water could be considered as the "perfect" hydrogen bonded system. Each Oygen (O) has 2 lone pairs of electrons therefore, 4 Hydrogen bonds (H-bonds) can be formed. Hydrogen-bonding network formed in liquid water is responsible for many of the essential and unique properties of water. Ice forms a crystalline lattice, held together by a multitude of H-bonds
Hydrogen Bonding in molecules the hydrogen is partially positive and attracted to the partially negative charge on the nitrogen. Nitrogen has only one lone pair, thus, only one hydrogen bond can be made to each nitrogen.