When this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion.

When applied to the simplest two-electron molecule, H < sub > 2 </ sub >, valence bond theory, even at the simplest Heitler-London approach, gives a much closer approximation to the bond energy, and it provides a much more accurate representation of the behavior of the electrons as chemical bonds are formed and broken.

When cells enter mitosis, the sister chromatids ( which represent the two copies of each chromosomal DNA molecule resulting from DNA replication earlier in the cell cycle and packaged by histones and other proteins into chromatin ) are linked all along their length by the action of the cohesin complex.

When an electron in an excited molecule or atom descends to a lower energy level, it emits a photon of light equal to the energy difference.

When oxygen is not bound, a very weakly bonded water molecule fills the site, forming a distorted octahedron.

When red cells reach the end of their life due to aging or defects, they are broken down in spleen, the hemoglobin molecule is broken up and the iron gets recycled.

When trying to define rigorously whether an arrangement of atoms is " sufficiently stable " to be considered a molecule, IUPAC suggests that it " must correspond to a depression on the potential energy surface that is deep enough to confine at least one vibrational state ".

When proteins bind specifically to other copies of the same molecule, they can oligomerize to form fibrils ; this process occurs often in structural proteins that consist of globular monomers that self-associate to form rigid fibers.

When the functional group attacking the peptide bond is a thiol, hydroxyl or amine, the resulting molecule may be called a cyclol or, more specifically, a thiacyclol, an oxacyclol or an azacyclol, respectively.

When a chlorophyll molecule at the core of the photosystem II reaction center obtains sufficient excitation energy from the adjacent antenna pigments, an electron is transferred to the primary electron-acceptor molecule, pheophytin, through a process called photoinduced charge separation.

When a ribosome finishes reading an mRNA molecule, these two subunits split apart.

When a molecule absorbs a quantum of energy that corresponds to a transition from one molecular orbital to another molecular orbital, the resulting electronic excited state is also properly described as an exciton.

When one water molecule is lost another is pulled along by the processes of cohesion and adhesion.

When the activation energy is given in molecular units instead of molar units, e. g., joules per molecule instead of joules per mole, the Boltzmann constant is used instead of the gas constant.

When the molecule relaxes it emits a photon and it returns to a different rotational or vibrational state.

When glycogen stores are not available in the cells, fat ( triacylglycerol ) is cleaved to provide 3 fatty acid chains and 1 glycerol molecule in a process known as lipolysis.

When meat is in its raw state, the iron atom is in the + 2 oxidation state, and is bound to a dioxygen molecule ( O < sub > 2 </ sub >).

When a faster-than-average molecule from A flies towards the trapdoor, the demon opens it, and the molecule will fly from A to B.

When this small molecule is water, it is known as a dehydration reaction ; other possible small molecules lost are hydrogen chloride, methanol, or acetic acid.

When the UV photon strikes a phosphor molecule, it momentarily raises the energy level of an outer orbit electron in the phosphor molecule, moving the electron from a stable to an unstable state ; the electron then sheds the excess energy as a photon at a lower energy level than UV light ; the lower energy photons are mostly in the infrared range but about 40 % are in the visible light range.

When a molecule absorbs a photon, it increases the energy of the molecule.

When " tripped ", it locks up solidly ( typically in a few to tens of milliseconds ) and rotates the driven member just one full turn.

When the trajectory r ( t ) rotates an amount dθ, u < sub > ρ </ sub >, which points in the same direction as r ( t ), also rotates by dθ.

When protecting the body, the boxer rotates the hips and lets incoming punches " roll " off the guard.

When descending a tree headfirst, the red panda rotates its ankle to control its descent, one of the few climbing species to do so.

When a body rotates while subject to tidal forces, internal friction results in the gradual dissipation of its rotational kinetic energy as heat.

When an electric current is applied, the galvanometer's indicator rotates and compresses a small spring.

When an object rotates about its axis, the motion cannot simply be analyzed as a particle, since in circular motion it undergoes a changing velocity and acceleration at any time ( t ).

When reading, the magnetized material rotates past the heads, the ferrite core concentrates the field, and a current is generated in the coil.

When the shutter release is pressed, a light-blocking shield lifts and the shutter disc rotates a full turn exposing the film through its open sector ; when the pressure is released the light-blocking shield returns to its position behind the lens, and the spring motor advances the film and recocks the shutter.

When the solenoid is activated, the core is drawn into the coil, and the disk rotates on the ball bearings in the grooves as it moves towards the coil body.

When power is removed, a spring on the disk rotates it back to its starting position, also pulling the core out of the coil.

When a disc is selected to be played, the carousel rotates so that the disc can be picked up by a pickup mechanism and placed in CD playback unit.

When a fluid rotates and viscous forces are balanced by the Coriolis effect ( rather than convective inertia ), an Ekman layer forms.

When it is turned on, it rotates and blows the soot off the tubes and out through the stack.

When an archerfish selects its prey, it rotates its eye so that the image of the prey falls on a particular portion of the eye in the ventral temporal periphery of the retina and its lips just break the surface, squirting a jet of water at its victim.

When reading data from a conventional electromechanical hard disk drive, the disk controller must first position the head, relatively slowly, to the track where a given fragment resides, and then wait while the disk platter rotates until the fragment reaches the head.

When the wheel rotates and stops with its arms in the vertical position it is possible for boats to enter and exit the lower caisson when the gates are open without flooding the docking-pit.

When acting alone it rotates to the opposite side ( contralaterally ) and slightly ( laterally ) flexes to the same side.

When the head rotates about any axis ( horizontal, vertical, or torsional ) distant visual images are stabilized by rotating the eyes about the same axis, but in the opposite direction.

When a patient is positioned for a radiographic image attempting to demonstrate Coxa Vara it is important that the technician insures that the patient medially rotates the foot 15 ° on the ipsilateral side ( same side ) being depicted in the film.

When the disk rotates through one complete revolution about a vertical axis, the wire unavoidably acquires a full twist.

When the board rotates more than 90 degrees and then returns to its original position over the course of the slide it is called a pendulum.

When the center of mass is placed in geostationary orbit then the cable rotates once per day with the Earth, and is usually referred to as a space elevator.