What are the Elements?

ELEMENTS 

Everything in the world is made from elements – pure substances that cannot be broken down into anything simpler. Elements can be grouped according to the properties they have in common, such as their appearance, how they conduct electricity, and how they react with other substances. There are nine main groups and the element hydrogen, which is unique.

  1. HYDROGEN Hydrogen makes up 90 per cent of all the matter in the Universe. Pure hydrogen is an invisible gas on Earth. It is not considered part of any one group. Hydrogen powers the nuclear reactions inside stars, including our Sun, and is found on Earth in the compound H2O or water.
  2. ALKALINE-EARTH METALS Alkaline-earth metals react with water and are found in minerals in Earth’s crust. In pure form, they are silvery-white. They are similar to alkali metals, but less reactive. Calcium, found in chalk, milk, and bones, is a member of this group.
  3. ALKALI METALS Sodium, contained in salt, is an alkali metal. These elements are characterized by their vigorous reaction with water. On contact, they will zoom all over the water’s surface or even explode. Alkali metals are not found in a pure form in nature because they react so strongly with water.
  4. TRANSITION METALS This group is the largest and includes iron, silver, gold, nickel, platinum, and titanium. Transition metals are considered typical metals – they are hard and shiny, conduct electricity and heat well, and have high melting points.
  5. ACTINIDES The elements in this group are radioactive metals mostly created synthetically in nuclear reactors or nuclear explosions. They have unstable atoms that break up and give out radiation particles. Uranium and plutonium are examples of actinides.
  6. LANTHANIDES These soft, reactive metals were known as rare earths, because they were wrongly believed to occur only scarcely in nature. Silvery-white in appearance, they tarnish easily on contact with air. Holmium, the element with the greatest magnetic strength, is in this group.
  7. NON-METALS Around one-sixth of elements are non-metals. They are poor conductors of electricity and melt at low temperatures. Carbon, nitrogen, and oxygen are all examples of non-metals, as are the halogens, a group of highly reactive elements that combine with other elements to form salts.
  8. NOBLE GASES There are seven noble gases – also called rare or inert gases because they do not readily react with anything or combine with other elements to make compounds. They are helium, neon, argon, krypton, xenon, radon, and oganesson, although the latter may be a solid at room temperature.
  9. POOR METALS Metals that are fairly soft and melt easily are known as poor metals. They are readily found as ores (minerals) in Earth and can be very useful, especially when made into alloys (two metals mixed together to make a harder metal). Aluminium and lead are both poor metals.
  10. SEMI-METALS These elements have some properties of metals and some of non-metals. Arsenic, for example, is shiny like a metal, but not a good conductor. Some semi-metals are semiconductors, behaving as conductors or insulators depending on what other substances are added to them.

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