transition element

Any chemical element with valence electrons in two shells instead of only one. This structure gives them their outstanding ability to form ions containing more than one atom (complex ions, or coordination compounds), with a central atom or ion (often of a transition metal) surrounded by ligands in a regular arrangement. Theories on the bonding in these ions are still being refined. The elements in the periodic table from scandium to copper (atomic numbers 21–29), yttrium to silver (39–47), and lanthanum to gold (57–79, including the lanthanide series) are frequently designated the three main transition series. (Those in the actinide series and beyond, 89–111, also qualify.) All are metals, many of major economic or industrial importance (e.g., iron, gold, nickel, titanium). Most are dense, hard, and brittle, conduct heat and electricity well, have high melting points, and form alloys with each other and other metals. Their electronic structure lets them form compounds at various valences. Many of these compounds are coloured and paramagnetic (see paramagnetism) and (as do the metals themselves) often act as catalysts. Seealso rare earth metal.

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Any of a large class of chemical elements including scandium (atomic number 21), yttrium (39), and the 15 elements from 57 (lanthanum) to 71 (see lanthanides). The rare earths themselves are pure or mixed oxides of these metals, originally thought to be quite scarce; however, cerium, the most plentiful, is three times as abundant as lead in the Earth's crust. The metals never occur free, and the pure oxides never occur in minerals. These metals are similar chemically because their atomic structures are generally similar; all form compounds in which they have valence 3, including stable oxides, carbides, and borides.

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In film editing, a wipe is a gradual spatial transition from one image to another. One image is replaced by another with a distinct edge that forms a shape. A simple edge, an expanding circle, or the turning of a page are all examples.

It is often acknowledged that using a wipe, rather than a simple cut or dissolve is a stylistic choice that inherently makes the audience more "aware" of the film as a film, rather than a story. For example, George Lucas is famous for the sweeping use of wipes in his Star Wars films, which help evoke a kinship to old pulp sci-fi novels and serials; he was inspired by a similar use of wipes by Akira Kurosawa.

The very earliest examples of a wipe are seen as long ago as 1903 in films like Mary Jane's Mishap by George Albert Smith.

Wipes also can be used as syntactic tools, but are often frowned on. Some examples are:

• An iris wipe is a wipe that takes the shape of a growing or shrinking circle. It has been frequently used in animated short subjects, such as those in the Looney Tunes and Merrie Melodies cartoon series, to signify the end of a story. When used in this manner, the iris wipe may be centered around a certain focal point and may be used as a device for a "parting shot" joke, a fourth wall-breaching wink by a character, or other purposes.
• A star wipe is a wipe that takes the shape of a growing or shrinking star, and is used to impart a sense of "extra specialness" or "added value." An example of the "star wipe" can be seen in the Guiding Light opening sequences of the 1980s. This convention was considered overused during that time period and is now generally thought to be somewhat out-of-date. The use was parodied in Aqua Teen Hunger Force Colon Movie Film for Theaters.
• A heart wipe is a wipe that takes the shape of a growing or shrinking heart, and is used to impart a sense of "love" or "friendship." The heart wipe is still used in wedding, graduation, and bar mitzvah videos, among others, as it has now passed from stylistic into the realm of standard convention, though many people consider it tacky.
• A matrix wipe is a patterned transition between two images. The matrix wipe can be various patterns such as a grid, stars, etc.
• A clock wipe is a wipe that sweeps a radius around the center point of the frame to reveal the subsequent shot, like the sweeping hands of an analog clock. Because of this similarity, it is often used to indicate that time has passed between the previous shot and the next shot.
• The most common uses of the wipe effect is the "Invisible Wipe" where a camera follows a person into another room by tracking parallel to the actor. As the wall pass in front of the camera, the editor has the option of using a wipe to be able to choose any other matching take of the same scene. It is also commonly used in quick camera pans in action sequences, to make a cut invisible. Such wipes can be impossible to see in the finished film. A good example of this wipe can be seen in the movie Das Boot when director Wolfgang Petersen uses it to pan between two occupied u-boat pens, even though they had only one u-boat for filming.
• Some extremely effective (and expensive) wipes were used in the otherwise very low-budget Laurel and Hardy short film Thicker Than Water. For each of the scene changes in this film, either Laurel or Hardy or both of them would seize a curtain or some other object at the edge of the frame and move it across the screen. The opening frames of the next scene were optically printed onto this object, so that -- when the object entirely filled the screen -- the movie had "wiped" the last shot of the previous scene and begun the first shot of the next.