Charge partial positive/negative

The symbols and indicate partial positive and partial negative charge respectively)... 

Adsorption of a neutral (n ) onto a metal surface leads to a heat of adsorption of Q, as the electrons and nuclei of the neutral and metal attract or repel each other. Partial positive and negative charges are induced on each with the formation of a dipolar field (Figure 7.4). 

An active-site zinc ion stabilizes negative charge development on the oxygen atom of acetaldehyde, leading to an induced partial positive charge on the carbonyl C atom. Transfer of the negatively charged hydride ion to this carbon forms ethanol. 

FIGURE 5.2 In water, ions are hydrated, (a) A cation is surrounded by waler molecules, oriented with their partially negatively charged oxygen atoms facing the ion. (b) An anion is surrounded by water molecules that direct their partially positively chaiged hydrogen atoms toward the ion. 

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