Arrow with half arrowhead

In this case, there are two arrows, each of which has its tail in the middle of the bond that is going to break. One arrow with half an arrowhead is going to one fluorine atom, while the other is going to the other. The half arrowhead indicates that only one electron is involved in each movement. This shows that the two electrons, which originally formed the single bond between the atoms, will be divided equally between the two fluorine atoms, with one electron going to each atom. 

Note that an arrow with only half of an arrowhead is used to show the movement of a single electron that occurs in radical reactions, whereas the normal arrow shows the movement of a pair of electrons. 

Throughout this chapter, we use curved red arrows to help us visualize the movement of electrons. lUPAC recommends the use of an arrow with a half arrowhead when a single electron is moved and an arrow with a full arrowhead when a pair of electrons is moved. 

By writing an equation for a reaction with double arrows, each with a half arrowhead ... 

Figure 9. The relationship between a half-turn and a node. A trefoil knot has been drawn with thick lines its polarity is shown by the arrowheads along the knot. A dashed box has been drawn about each node, so that the strands of the knot divide the boxes into four regions, two between antiparallel strands, two between parallel strands. A half-turn of base pairs is drawn between antiparallel strands the helix axes are shown as double-headed arrows and dyad axes normal to them are represented by dotted lines ending in two ellipses.

Figure 11.2. Scanning electron micrographs of full-fat (33.0%, w/w A, D) half-fat (17.0%, w/ w B, E) and low-fat (3.9% w/w C, F) Cheddar cheese at low (A, B, C) or high (D, E, F) magnifications. The arrows indicate the para-casein matrix and the arrowheads the areas occupied by fat and free serum prior to their removal during sample preparation [modified from Guinee et al., 1998 (a, b, d, e) and Fenelon et al., 1999 (c, f) with permission].

Note that only one arrow is used, and that it has a complete arrowhead, which represents the two electrons in the bond. It is not necessary to use two arrows, each with only half an arrowhead, because the two electrons are moving together. The tail of the arrow is on the bond that is about to break, and the head is on the chlorine atom, which is the destination of the electrons. Note that the Conservation of Charge is obeyed by the formation of the monocation and the monoanion. This type of bond cleavage is called heterolytic fission. 

Fig. 85. A. Drawing displaying the distribution of mossy rosettes (dots) immunoreactive to monoclonal choline-acetyltransferase (ChAT) antibody. The section (40 fim thick) was cut sagittally through the middle vermis of rat cerebellum. A considerable number of immunoreactive mossy terminals are observed in lobules I through IXab, although they are much fewer than in lobules IXc and X. Calibration bar = 1 mm. B. Drawing of part of lobule IXab shows the overall distribution of immunoreactive fibers. Arrows indicate mossy fibers with glomerular rosettes. Small and large arrowheads point to some varicose fibers distributing in or near the Purkinje cell layer (PCL) and in the molecular layer (ML), respectively. The ML fibers are most frequently observed in this lobule and tend to be restricted to the inner half of the layer. Calibration bar = 200 jum. Ojima et al. (1989).

Fig. 17.35. Surgical fasciotomy. Long-axis 12-5 MHz US image obtained over the posterior half of the plantar fascia 12 months after open fasciotomy shows a persistent gap (arrowheads) in the plantar fascia (white arrows) filled with hypoechoic tissue (asterisk) suggesting perifascial fibrosis. Note the fasciotomy scar (open arrow) in the subcutaneous fat. C, calcaneus...

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