Arrange the stages of the Gurney-Mott mechanism in the order they occur.

1. A photon is absorbed and frees an electron inside the crystal
2. The electron is trapped at a sensitivity speck, which becomes negatively charged
3. A mobile interstitial silver ion is attracted to the charged speck
4. The ion is neutralised and becomes a silver atom on the speck
5. The cycle repeats until the speck is large enough to be developable

The alternation of an electronic step and an ionic step is what makes the mechanism work at all: the electron moves fast and does the trapping, the silver ion moves slowly and does the building. Reversing them would require an ion to arrive before there was any charge to attract it.