Elements

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Elements

Chemical element, also called element, any substance that cannot be decomposed into simpler substances by ordinary chemical processes. Elements are the fundamental materials of which all matter is composed.

At present there are 118 known chemical elements. About 20 percent of them do not exist in nature (or are present only in trace amounts) and are known only because they have been synthetically prepared in the laboratory. Of the known elements, 11 (hydrogen, nitrogen, Oxygen, fluorine, chlorine, and the six noble gases) are gases under ordinary conditions, two (bromine and mercury) are liquids (two more, cesium and gallium, melt at about or just above room temperature), and the rest are solids. Elements can combine with one another to form a wide variety of more complex substances called compounds.

The number of possible compounds is almost infinite; perhaps a million are known, and more are being discovered every day. When two or more elements combine to form a compound, they lose their separate identities, and the product has characteristics quite different from those of the constituent elements. The gaseous elements hydrogen and oxygen, for example, with quite different properties, can combine to form the compound water, which has altogether different properties from either oxygen or hydrogen. Water clearly is not an element because it consists of, and actually can be decomposed chemically into, the two substances hydrogen and oxygen; these two substances, however, are elements because they cannot be decomposed into simpler substances by any known chemical process. Most samples of naturally occurring matter are physical mixtures of compounds. Seawater, for example, is a mixture of water and a large number of other compounds, the most common of which is sodium chloride, or table salt. Mixtures differ from compounds in that they can be separated into their component parts by physical processes; for example, the simple process of Evaporation separates water from the other compounds in seawater.

 

 

The Atomic Nature Of The Elements

Paralleling the development of the concept of elements was an understanding of the nature of matter. At various times in history, matter has been considered to be either continuous or discontinuous. Continuous matter is postulated to be homogeneous and divisible without limit, each part exhibiting identical properties regardless of size. This was essentially the point of view taken by Aristotle when he associated his elemental qualities with continuous matter. Discontinuous matter, on the other hand, is conceived of as particulate—that is, divisible only up to a point, the point at which certain basic units called atoms are reached. According to this concept, also known as the atomic hypothesis, subdivision of the basic unit (atom) could give rise only to particles with profoundly different properties. Atoms, then, would be the ultimate carriers of the properties associated with bulk matter.

The atomic hypothesis is usually credited to the Greek philosopher Democritus, who considered all matter to be composed of atoms of the four elements—earth, air, fire, and water. But Aristotle’s concept of continuous matter generally prevailed and influenced thought until experimental findings in the 16th century forced a return to the atomic theory. Two types of experimental evidence gave support to the atomic hypothesis: first, the detailed behaviour of gaseous substances and, second, the quantitative weight relationships observed with a variety of chemical reactions. The English chemist John Dalton was the first to explain the empirically derived laws of chemical combination by postulating the existence of atoms with unique sets of properties. At the time, chemical combining power (valence) and relative atomic weights were the properties of most interest. Subsequently numerous independent experimental verifications of the atomic hypothesis were carried out, and today it is universally accepted. Indeed, in 1969 individual uranium and thorium atoms were actually observed by means of an electron Microscope.

Mixtures

Mixtures are absolutely everywhere you look. Most things in nature are mixtures. Look at rocks, the ocean, or even the Atmosphere. They are all mixtures, and mixtures are about physical properties, not chemical ones. That statement means the individual Molecules enjoy being near each other, but their fundamental chemical structure does not change when they enter the mixture. If the chemical structure changed, it would be called a reaction.

There are an infinite number of mixtures. Anything you can combine is a mixture. Think of everything you eat. Just think about how many cakes there are. Each of those cakes is made up of a different mixture of ingredients. Even the wood in your pencil is considered a mixture. There is the basic cellulose of the wood, but there are also thousands of other compounds in that pencil. solutions are also mixtures, but all of the molecules are evenly spread out through the system. They are called homogenous mixtures.

If you put sand into a glass of water, it is considered to be a mixture. You can always tell a mixture, because each of the substances can be separated from the group in different physical ways. You can always get the sand out of the water by filtering the water away. If you were busy, you could just leave the sand and water mixture alone for a few minutes. Sometimes mixtures separate on their own. When you come back, you will find that all of the sand has sunk to the bottom. Gravity was helping you with the separation. Don’t forget that a mixture can also be made of two liquids. Even something as simple as oil and water is a mixture.

Alloys

There are a few more words you might hear when people talk about mixtures. We can’t cover all of them, but we’ll give you a quick overview of the biggies. Alloys are basically a mixture of two or more metals. Don’t forget that there are many elements on the periodic table. Elements like calcium (Ca) and potassium (K) are considered metals. Of course, there are also metals like silver (Ag) and gold (Au). You can also have alloys that include small amounts of non-metallic elements like carbon (C). Metals are the key thing to remember for alloys.

 

Emulsions

Let’s finish up with a little information on emulsions. These special colloids (another type of mixture) have a mixture of oils and waters. Think about a bottle of salad dressing. Before you mix it, there are two separate layers of liquids. When you shake the bottle, you create an emulsion. As time passes, the oil and water will separate, because emulsions are mixtures.


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What are the different types of elements?

There are 118 elements in the periodic table, which is a chart of all the known elements. The elements are arranged in order of their atomic number, which is the number of protons in the nucleus of an atom. The elements are also grouped into columns called groups and rows called periods.

What are the properties of elements?

The properties of elements are determined by the number of protons and electrons in their atoms. The number of protons determines the element’s atomic number, and the number of electrons determines the element’s chemical properties.

What are some examples of elements?

Some examples of elements are hydrogen, helium, lithium, sodium, potassium, calcium, magnesium, iron, copper, zinc, tin, lead, gold, silver, platinum, and uranium.

What are the uses of elements?

Elements are used in a variety of products and applications. Some common uses of elements include:

  • Hydrogen: fuel for rockets and other spacecraft
  • Helium: used in balloons and blimps
  • Lithium: used in batteries
  • Sodium: used in table salt
  • Potassium: used in Fertilizers
  • Calcium: used in construction materials
  • Magnesium: used in alloys
  • Iron: used in steel
  • Copper: used in electrical wiring
  • Zinc: used in batteries
  • Tin: used in cans
  • Lead: used in batteries and ammunition
  • Gold: used in jewelry and coins
  • Silver: used in jewelry and silverware
  • Platinum: used in jewelry and catalytic converters
  • Uranium: used in nuclear power Plants

What are the dangers of elements?

Some elements can be dangerous if they are not handled properly. For example, hydrogen is flammable, and helium can cause asphyxiation. Other elements, such as lead and uranium, are radioactive and can cause cancer.

What are the future of elements?

The future of elements is uncertain. Some scientists believe that we will eventually run out of certain elements, such as lithium and cobalt. Others believe that we will find new ways to extract elements from the Earth or from asteroids.

Sure, here are some MCQs without mentioning the topic “Elements”:

  1. Which of the following is not a chemical element?
    (A) Hydrogen
    (B) Oxygen
    (C) Water
    (D) Carbon

  2. Which of the following is the most abundant element in the universe?
    (A) Hydrogen
    (B) Helium
    (C) Oxygen
    (D) Carbon

  3. Which of the following is the most abundant element in the Earth’s crust?
    (A) Oxygen
    (B) Silicon
    (C) Aluminum
    (D) Iron

  4. Which of the following is the most abundant element in the human body?
    (A) Oxygen
    (B) Carbon
    (C) Hydrogen
    (D) Nitrogen

  5. Which of the following is the most reactive element?
    (A) Hydrogen
    (B) Fluorine
    (C) Chlorine
    (D) Bromine

  6. Which of the following is the least reactive element?
    (A) Helium
    (B) Neon
    (C) Argon
    (D) Krypton

  7. Which of the following is a Metal?
    (A) Hydrogen
    (B) Oxygen
    (C) Carbon
    (D) Silicon

  8. Which of the following is a non-metal?
    (A) Iron
    (B) Copper
    (C) Gold
    (D) Carbon

  9. Which of the following is a metalloid?
    (A) Silicon
    (B) Germanium
    (C) Arsenic
    (D) Selenium

  10. Which of the following is an Alloy?
    (A) Steel
    (B) Brass
    (C) Bronze
    (D) All of the above

  11. Which of the following is a compound?
    (A) Water
    (B) Carbon dioxide
    (C) Sugar
    (D) All of the above

  12. Which of the following is an element?
    (A) Hydrogen
    (B) Oxygen
    (C) Carbon
    (D) All of the above

  13. Which of the following is a mixture?
    (A) Air
    (B) Seawater
    (C) Soil
    (D) All of the above

  14. Which of the following is a solution?
    (A) Salt water
    (B) Sugar water
    (C) Vinegar
    (D) All of the above

  15. Which of the following is a suspension?
    (A) Mud
    (B) Paint
    (C) Blood
    (D) All of the above

  16. Which of the following is a colloid?
    (A) Milk
    (B) Mayonnaise
    (C) Fog
    (D) All of the above

  17. Which of the following is a pure substance?
    (A) Water
    (B) Salt
    (C) Sugar
    (D) All of the above

  18. Which of the following is a heterogeneous mixture?
    (A) Air
    (B) Seawater
    (C) Soil
    (D) All of the above

  19. Which of the following is a homogeneous mixture?
    (A) Salt water
    (B) Sugar water
    (C) Vinegar
    (D) All of the above

  20. Which of the following is a physical change?
    (A) Water boiling
    (B) Ice melting
    (C) Wood burning
    (D) All of the above

  21. Which of the following is a chemical change?
    (A) Rusting of iron
    (B) Cooking of food
    (C) Burning of wood
    (D) All of the above

  22. Which of the following is a physical property?
    (A) Density
    (B) Melting point
    (C) Boiling point
    (D) All of the above

  23. Which of the following is a chemical property?
    (A) Flammability
    (B) Reactivity
    (C) Corrosivity
    (D) All of the above

  24. Which of the following is a physical change that can be reversed?
    (A) Water boiling
    (B) Ice melting
    (C) Wood burning
    (D) None of the above

  25. Which of the following is a chemical change that can be reversed?
    (A) Rusting of iron
    (B) Cooking of food
    (C) Burning of wood
    (D) None of the above

I hope these MCQs are helpful!