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The electron configuration 1S22s22p63s23p6fits all of the following ions except one．The exception is( )。
A．P3-B．K+C．Cl-D．Mg2+
答案
更多“The electron configuration 1S22s22p63s23p6 fits all of the following ions except one．The exception i”相关的问题
第1题
Such electron tubes ______ in a radio set are also found in a TV set.
A．that we use
B．as we use
C．as we use them
D．that we use them
第3题
第4题
A．see viruses directly
B．develop the electron microscope later on
C．understand more about the distribution of the chemical elements
D．discover single-celled plants anal animals they had never seen before
第5题
A．They will probably replace electron microscopes altogether.
B．They will eventually he much cheaper to produce than they are now.
C．They will provide information not available from other kinds of microscopes.
D．They will eventually change the illumination range that they now use.
第6题
Each advance in microscopic technique has provided scientists with new perspectives on the function of living organisms and the nature of matter itself. The invention of the visible-light microscope late in the sixteenth century introduced a previously unknown realm of single celled plants and animals. In the twentieth century, electron microscope have provided direct views of viruses and minuscule surface structures. Now another type of microscope, one that utilizes X rays rather than light or electrons, offers a different way of examining tiny de tails; it should extend human perception still farther into the natural world.
The dream of building an X-ray microscope dates to 1895; its development, however, was virtually halted in the 1940's because the development of the electron microscope was progressing rapidly. During the 1940's, electron microscopes routinely achieved resolution better than that possible with a visible-light microscope, while the performance of X-ray microscopes resisted improvement. In recent years, however, interest in X-ray microscopes has revived, largely because of advances such as the development of new sources of X-ray illumination. As a result, the brightness available today is millions, of times that of X-ray tubes, which, for most of the century, were the only avail able sources of soft X-rays.
The new X-ray microscopes considerably improve on the resolution provided by optical microscopes. They can also be used to map the distribution of certain chemical elements. Some can form. pictures in extremely short times; others hold the promise of special capabilities such as three-dimensional imaging. Unlike conventional electron microscopy, X-ray microscopy enables specimens to be kept in air and in water, which means that biological samples can be studied under conditions similar to their natural state. The illumination used, so-called soft X rays in the wavelength range of twenty to forty angstroms (an angstrom is one ten-billionth of a meter), is also sufficiently penetrating to, image intact biological cells in many cases. Because of the wavelength of the X rays used, soft X-ray microscopes will never match the highest resolution possible with electron microscopes. Rather, their special properties will make possible investigations that will complement those performed with light-and-electron-based instruments.
What does the passage mainly discuss？
A．The detail seen through a microscope.
B．Sources of illumination for microscopes.
C．A new kind of microscope.
D．Outdated microscopic techniques.
第7题
Dr. Conrad and William C. Louis presented their initial findings in a talk yesterday at the Fermi National Accelerator Laboratory where the experiment is being performed.
The goal was to confirm or refute observations made in the 1990s in a Los Alamos experiment that observed transformations in the evanescent but bountiful particles known as neutrinos(微中子). Neutrinos have no electrical charge and almost no mass, but there are so many of them that they could collectively outweigh all the stars in the universe.
The new experiment has attracted wide interest. That reflected in part the hope of finding cracks in the Standard Model, which encapsulates physicists' current knowledge about fundamental particles and forces.
The Standard Model has proved remarkably effective and accurate, but it cannot answer some fundamental questions, like why the universe did not completely annihilate(毁灭) itself an instant after the Big Bang.
The birth of the universe 13.7 billion years ago created equal amounts of matter and antimatter. Since matter and antimatter annihilate each other when they come in contact, that would have left nothing to coalesce into stars and galaxies. There must be some imbalance in the laws of physics that led to a slight preponderance of matter over antimatter, and that extra bit of matter formed everything in the visible universe.
The imbalance, some physicists believe, may be hiding in the dynamics of neutrinos.
Neutrinos come in three known types, or flavors. And they can change flavor as they travel. But the neutrino transformations reported in the Los Alamos data do not fit the three-flavor model, suggesting four flavors of neutrinos, if not more.
The new experiment sought to count the number of times one flavor of neutrino, called a muon(μ介子), turned into another flavor, an electron neutrino.
For most of the neutrino energy range they looked at, the scientists did not see any more electron neutrinos than would be predicted by the Standard Model. That ruled out the simplest ways of interpreting the Los Alamos neutrino data, Dr. Conrad and Dr. Louis said.
But at the lower energies, the scientists did see more electron neutrinos than predicted: 369, rather than the predicted 273. That may simply mean that some calculations are off. Or it could point to a subtler interplay of particles, known and unknown.
Dr. Louis said he was surprised by the results". I was sort of expecting a clear excess or no excess", he said. "In a sense, we got both".
It can be inferred from Paragraph 1 that the" initial findings" of Dr. Conrad and Louis are ______.
A．a new class of subatoms.
B．new subatomic particles.
C．new characters of neutrinos.
D．none of the above.
第8题
More than 40 years passed before physicists were able to offer an explanation for superconductivity. The accepted theory, developed in the 1950s, holds that the fundamental behavior. of electrons changes at very low temperatures because of the effects of quantum mechanics. Electrons are tiny particles that make up the outer part of an atom, circling rapidly around the nucleus of the atom. In a regular conductor—a metal that conducts an electric current—the outermost electrons are not bound tightly to the atoms, and so they move around relatively freely. The flow of these electrons is an electric current.
At normal temperatures, a conductor's electrons cannot move completely freely through the metal because they are "bumped around" by the metal's atoms. But according to the leading theory of superconductivity, when a metal is very cold, electrons form. pairs. Then, like couples maneuvering on a crowded dance floor but never colliding, the paired electrons are able to move unimpeded through the metal. In pairing up, it seems, the electrons are able to "blend together" and move in unison without resistance. This explanation seems to account for superconductivity at extremely low temperatures, but in 1986 scientists in Switzerland found that some metal-containing ceramics are superconductors at much higher temperatures. By 1992, scientists had developed ceramics that become superconducting at - 297'F, and some researchers speculated that room-temperature superconductors may be possible. Scientists are still trying to formulate a theory for high-temperature superconductivity.
The new ceramic materials can be maintained at their superconducting temperatures, with relatively inexpensive liquid nitrogen rather than the much colder and much more costly liquid helium required by metal superconductors. The cost difference could make superconductivity practical for many new technologies. For example, magnetically levitated trains, which require superconducting electromagnets, would be much cheaper to build than they are now. Superconducting devices might also be used for advanced power transmission lines and in new types of compact, ultrafast computers. But for the time being, superconductivity is finding application mostly in scientific research and in some kinds of medical imaging devices.
The flow of an electric current in a regular conductor is made possible by the fact that______.
A．electrons circle rapidly around the atom
B．the outermost electron move relatively freely around the atom
C．the innermost electrons stick to the atom
D．the outermost electrons are bound tightly to the inner ones
第9题
Part A
Directions: Read the following four texts. Answer the questions below each text by choosing A, B, C or D. (40 points)
The unknown pervades the universe. That which people can see, with the aid of various sorts of telescope, accounts for just 4% of the total mass. The rest, however, must exist. Without it, galaxies would not survive and the universe would not be gently expanding, as witnessed by astronomers. What exactly constitutes this dark matter and dark energy remains mysterious, but physicists have recently uncovered some more clues, about the former, at least.
One possible explanation for dark matter is a group of subatomic particles called neutrinos. Neutrinos are thought to be the most abundant particles in the universe. According to the Standard Model, the most successful description of particle physics to date, neutrinos come in three varieties, called "flavors". Again, according to the Standard Model, they are point-like, electrically neutral and massless. But in recent years, this view has been challenged, as physicists realized that neutrinos might have mass.
The first strong evidence came in 1998, when researchers at an experiment, based in Japan, showed that muon neutrinos produced by cosmic rays hitting the upper atmosphere had gone missing by the time they should have reached an underground detector. Its operators suspect that the missing muon neutrinos had changed flavor, becoming electron neutrinos or-more likely-tau neutrinos. Theo- ry suggests that this process, called oscillation, can happen only if neutrinos have mass.
Over the coming months and years, researchers hope to produce the most accurate measurements yet. The researchers created a beam of muon neutrinos first. On the other side of the target sat a particle detector that monitored the number of muon neutrinos leaving. The neutrinos then travelled 750km (450 miles) through the Earth to a detector in a former iron mine in Soudan, Minnesota. Researchers then were able to confirm that a significant number of muon neutrinos had disappeared-that is, they had changed flavor. While their mass is so small that neutrinos cannot be the sole constituent of dark matter, they have an advantage in that they are at least known to exist.
The same cannot be said for sure of another possible form. of dark matter being studied by a group of physicists in Italy. If the result continues to withstand scrutiny, it would appear to be evidence for an exotic new sort of fundamental particle, known as an axion, which could also be a type of dark matter.
What does the word "pervades"(Line 1, Para. 1) mean？
A．Be of higher rank or authority.
B．To spread through the whole extent of.
C．To gain the victory or superiority.
D．To make something come true.
