Chemical Elements and the Water Cycle: A Comprehensive Guide
Chemical Elements
A chemical element is a substance that cannot be broken down into simpler substances. There are over 100 chemical elements, but only 90 occur naturally. The remaining elements have been created by humans in nuclear reactors.
Each element has a unique name and symbol. The symbol may be a capital letter, a capital letter followed by a lowercase letter, or derived from the element’s name.
The ability of elements to combine with each other to form different substances is called valence. Valence can be metallic or nonmetallic. All elements have one or more valence electrons, but only metals have a single valence electron.
Examples of Chemical Elements
- Hydrogen (H)
- Lithium (Li)
- Sodium (Na)
- Potassium (K)
- Rubidium (Rb)
- Cesium (Cs)
- Francium (Fr)
- Beryllium (Be)
- Magnesium (Mg)
- Calcium (Ca)
- Strontium (Sr)
- Barium (Ba)
- Radium (Ra)
- Scandium (Sc)
- Yttrium (Y)
- Lanthanum (La)
- Actinium (Ac)
- Titanium (Ti)
- Zirconium (Zr)
- Hafnium (Hf)
- Vanadium (V)
- Niobium (Nb)
- Tantalum (Ta)
- Chromium (Cr)
- Molybdenum (Mo)
- Tungsten (W)
- Manganese (Mn)
- Technetium (Tc)
- Rhenium (Re)
- Iron (Fe)
- Ruthenium (Ru)
- Osmium (Os)
- Cobalt (Co)
- Rhodium (Rh)
- Iridium (Ir)
- Nickel (Ni)
- Palladium (Pd)
- Platinum (Pt)
- Copper (Cu)
- Silver (Ag)
- Gold (Au)
- Zinc (Zn)
- Cadmium (Cd)
- Mercury (Hg)
- Boron (B)
- Aluminum (Al)
- Gallium (Ga)
- Indium (In)
- Thallium (Tl)
- Carbon (C)
- Silicon (Si)
- Germanium (Ge)
- Tin (Sn)
- Lead (Pb)
- Nitrogen (N)
- Phosphorus (P)
- Arsenic (As)
- Antimony (Sb)
- Bismuth (Bi)
- Oxygen (O)
- Sulfur (S)
- Selenium (Se)
- Tellurium (Te)
- Polonium (Po)
- Helium (He)
- Neon (Ne)
- Argon (Ar)
- Krypton (Kr)
- Xenon (Xe)
- Radon (Rn)
The Water Cycle
Water covers about 71% of the Earth’s surface. Water can be divided into two groups: marine waters and inland waters.
Marine Waters
Marine waters include the seas and oceans, which cover over 97% of the Earth’s water. Marine waters are salty.
Inland Waters
Inland waters include rivers, lakes, ice, and groundwater. Inland waters represent just under 3% of the Earth’s water. Inland waters are generally freshwater, meaning they contain less salt than marine waters.
Water is constantly circulating through the water cycle. The water cycle is the process by which water moves from the Earth’s surface to the atmosphere and back again.
Rivers
A river is a permanent stream of water that flows through a channel. Rivers are formed when water from rain or snowmelt collects in a low-lying area and begins to flow downhill.
The source of a river is the point where it begins to flow. The mouth of a river is the point where it empties into a larger body of water, such as a lake or ocean.
Rivers are important for human life. We use rivers for transportation, irrigation, and drinking water.
The Course of a River
The course of a river is the path that it takes from its source to its mouth. Rivers have different lengths. The Nile River in Africa is the longest river in the world.
There are three main stages in the course of a river:
- Upper course: The upper course of a river is the area where it begins to flow. The upper course is typically mountainous, and the water flows quickly.
- Middle course: The middle course of a river is the area where it flows through a valley. The middle course is typically less steep than the upper course, and the water flows more slowly.
- Lower course: The lower course of a river is the area where it flows into a larger body of water. The lower course is typically flat, and the water flows very slowly.
The Flow of a River
The flow of a river is the amount of water that it carries. The flow of a river can vary depending on the season. Rivers typically have a higher flow during the rainy season than during the dry season.
The Hydrosphere
The hydrosphere is the part of the Earth that is covered by water. The hydrosphere includes the oceans, seas, lakes, rivers, and groundwater.
The hydrosphere is important for life on Earth. Water is essential for all living things. The hydrosphere also helps to regulate the Earth’s climate.
The Atmosphere
The atmosphere is the layer of gases that surrounds the Earth. The atmosphere is composed of nitrogen, oxygen, and other gases.
The atmosphere is important for life on Earth. The atmosphere protects the Earth from harmful radiation from the sun. The atmosphere also helps to regulate the Earth’s temperature.