Study Guide

The Periodic Table Themes

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  • Semiconductors

    The What, Whys, and Hows of Semiconductors

    We've already learned about metalloids and how they're also known as semiconductors, but what is a semiconductor? Inquisitive minds want to know.

    Metals are good conductors. This means heat and electricity can flow through them easily. Non-metals are not good conductors. What about the elements that are neither metal nor non-metal? The metalloids, as they are called, can sometimes act as a conductor while other times it cannot. This ability to "turn on" or "turn off" conductivity is the basis of being a semiconductor.

    Check out a semiconductor chip here.

    A semiconductor is a material that has mild conductivity compared to a metal. Don't let that stop them from doing their thing. Because their conductivity is lower than that of metals, the semiconductor wizards have found that their conductivity can be turned on and off. This special conductivity behavior allows us to manipulate how, where, and when electrons flow. We (along with our iPhones) are the masters of electron.

    See another semiconductor chip here.

    Being able to control electron flow is the foundation of modern electronics. We would be sad if semiconductors did not exist. No TV. No radio. No computer. No iPad. No fun. Want to learn more about the physics of semiconductors? Check out this website.

    Currently most semiconductor devices are composed of silicon (Si). Have you ever wondered where or what Silicon Valley is? No, it's not some mythical stash of elemental silicon tucked in between two mountains. It's actually a place near San Francisco where a lot of technology companies were founded. These companies have revolutionized the world of electronics thanks to silicon and other semiconductors.

    See the Silicon Valley and some of the companies that are located there here.

    The pioneers of semiconductor research were William Bradford Shockley, John Bardeen, and Walter Houser Braittain. They won a Nobel Prize in 1956 (Physics)"for their researches on semiconductors and their discovery of the transistor effect."16 Check out more about their award winning work here.

  • The Carbon Cycle

    Carbon is Nature's favorite Lego piece. Nature uses carbon in virtually all forms of life on Earth. Fortunately carbon is one of the most abundant elements on our planet so there is plenty of life to be lived. Like all matter though, carbon cannot be created nor destroyed. So what happens to the carbon when something dies? The answer is the carbon cycle.

    The Carbon Cycle

    There is a fixed amount of carbon on the planet. It's found in both living and non-living things. We call these living carbon-containing things organic. The non-living objects are called inorganic and are things like rocks, shells, the atmosphere, and oceans. Carbon is pretty much everywhere.

    One of the most important forms of carbon is carbon dioxide (CO2). It's a vital and essential component of our atmosphere. It prevents heat from escaping Earth and warms up the atmosphere. For this reason CO2 is called a greenhouse gas because it makes Earth act like a giant greenhouse.

    Carbon dioxide is a greenhouse gas. Want to see a greenhouse? Click here.

    How does carbon get from point A to point B? How does it go from being inside an organic thing to an inorganic thing? Carbon moves through the Earth's system from living to non-living things in many different ways. In a sense, the Earth has a fantastic recycling program set up for its favorite element. This natural recycling program is the carbon cycle.

    The Carbon Cycle

    Basically the Earth has tons of different way to push carbon from one system to another. These methods include photosynthesis, animal respiration, plant respiration, and the decay process. There are tons of options in Nature.
    Here's an example. Plants use sunlight and carbon dioxide from the atmosphere to make their own food and grow. The carbon is now a part of the plant. At some point the plant will die and decay (or get eaten by another organism). Plants that die and are buried may turn into fossil fuels like coal or natural gas. We humans, in turn, burn that fossil fuel and put the carbon back into the atmosphere. Talk about coming full circle.

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