Low clouds
Stratus clouds are uniform grayish clouds that often cover the sky. Usually no precipitation falls from stratus clouds, but they may drizzle. When a thick fog “lifts,” the resulting clouds are low stratus. Nimbostratus clouds form a dark gray, “wet” looking cloudy layer associated with continuously falling rain or snow. They often produce light to moderate precipitation.
Middle clouds
Clouds with the prefix “alto” are middle-level clouds that have bases at 6,500 to 23,000 feet up. Altocumulus clouds are made of water droplets and appear as gray, puffy masses, sometimes rolled out in parallel waves or bands. These clouds on a warm, humid summer morning often mean thunderstorms by late afternoon. Altostratus clouds, gray or blue-gray, are made up of ice crystals and water droplets. They usually cover the sky. In thinner areas of them, the sun may be dimly visible as a round disk. Altostratus clouds often form ahead of storms that produce continuous precipitation.
High clouds
Cirrus clouds are thin, wispy clouds blown by high winds into long streamers. They are considered “high clouds,” forming at more than 20,000 feet. They usually move across the sky from west to east and generally mean fair to pleasant weather. Cirrostratus, thin, sheetlike clouds that often cover the sky, are so thin the sun and moon can be seen through them. Cirrocumulus clouds appear as small, rounded white puffs. Small ripples in the cirrocumulus sometimes resemble the scales of a fish, creating what is sometimes called a “mackerel sky.”
Vertical clouds
Cumulus clouds are puffy and can look like floating cotton. The base of each is often flat and may be only 330 feet above ground. The top has rounded towers. When the top resembles a cauliflower head, it is called “cumulus congestus.” These grow upward and if they continue to grow vertically can develop into a giant cumulonimbus, a thunderstorm cloud, with dark bases no more than 1,000 feet above ground and extending to more than 39,000 feet. Tremendous energy is released by condensation of water vapor in a cumulonimbus. Lightning, thunder and violent tornadoes are associated with them.
The elements in the periodice table are not listed in alphabetical order, because the arragement in rows (periods) and columns (groups or familes), in increasing order of atomic number (number of protons of the atoms) permits to explain similarities among the elements, trend in some properties, and even predict properties of unknown elements.
For example, the elements of the first group (family), called alkaline metals, all have 1 valence electron, have similar physical properties (ductibility, malleability, luster, thermal and electricity conductivity), react in similar way with water, show a trend in the atomic radii and in the ionization energy.
You can tell similar stories for other groups like, alkalyne earth metals, halogens and noble gases.
You can also tell trends in electroneativities, and atomic radii, for a row of elements, as per the order they are in the row.
So, the current array resulted very helpul for chemists to explain and predict the behavior and properties of the elements.
The answer is
a symmetrical molecule.
