METALS AND NONMETALS

             Elements are the simplest form of substances. This means that whatever you do with an element, it remains to be the same element. Its physical state may change but the identity of the element will not. It may form compounds with other elements but the element will never form anything simpler than it already is.
There are already more than a hundred elements and are organized in a Periodic Table. Some of them are naturally occurring and some were produced in a laboratory.

         In this module, you will find out more about the elements. You will see that majority of them are metals, and almost the rest are nonmetals.

How are metals different from nonmetals?
How are they similar?

           In the earlier grades, you segregated objects according to the material they are made of. You did this when you were starting the habit of 5Rs — recycle, reuse, recover, repair or reduce. Look around you. Which objects are made of metals? What made you say that they are metals?

          Perhaps, you have been identifying a metal based on its appearance. Most of the time, metals are shiny. They exhibit a certain luster.

Other properties exhibited by some metals
             Some metals are ductile. This means that metals can be drawn into wires. An example is copper. Refer to the figure on the right. Note the form at which copper is mined. However, due to its ductility, copper may assume a form similar to a wire, just like the image in the cover of this module. Gold is also a metal that is ductile; however, it is rarely used as an electrical wire. What could be the reason for this?

             Some metals are malleable. This means that they can be hammered or rolled into thin sheets without breaking. An example is aluminum. It is mined deep from the ground in the form of blocks. They are passed into mills and rolled thinly. One common form is the aluminum foil that you use to wrap food to keep it hot. Most soda cans are made of aluminum too. Find a soda can and strike it with a hammer. What happened with the soda can?

             Some metals are magnetic. This means that they are attracted by a magnet. The common ones are iron, nickel and cobalt. Get a magnet. Try them in different metals in your home or school. Were they all attracted to the magnet? What metals are these?

             Metals are known to possess luster, ductility, malleability and magnetic properties. However not all metals exhibit all of these properties. For instance, the metals sodium and potassium are not ductile at ordinary conditions. They are very soft that even a kitchen knife can cut them into slices as what you can see in the image on the right. Note though that only experts are allowed to do this. Recall what you have learned in module 4 about sodium when it comes in contact with water. Zinc at room temperature is not malleable. Most of the metals are not attracted by a magnet. Nevertheless, a material is still considered a metal as long as it possesses any of these properties. A material that does not possess any of these properties is known as a nonmetal.

 Properties exhibited by all metals
         But are there properties that are common to all metals?

         Electrical conductivity is property of metals that allows electricity to pass through a material.

           The metallic probe in the figure on the right is the one that comes in contact with the sample. It will measure then display the electrical conductivity value in the liquid crystal display (LCD) screen. Refer to the periodic table found at the back page of this module. The electrical conductivity values are written at the bottom line of each box. It is expressed in x106 Ohm-1cm-1. What do you notice about the elements with electrical conductivity values? Where are they located in the periodic table?

            One amazing feature of the periodic table is that all the metals are placed in one side. Those that are on the other side (grayish  shade) are the nonmetals.

        Notice that there is a stair step line which somewhat divides the metals and nonmetals. These elements are the metalloids. They are elements exhibiting properties that are intermediate to metals and nonmetals. Name the metalloids. Name some metals. Name some nonmetals.

           Which are electrically conductive, metals or nonmetals? Which element has the highest electrical conductivity value? Is it higher than copper? If so, what could be the reason for using copper as an electrical wire more than this element?

           You might wonder why some metals do not have electrical conductivity values when supposedly all of them possess such property. Notice that these metals are the ones mostly found at the last rows of the periodic table. Elements in those rows are mostly radioactive. This means that the element is very unstable and exists in a very short period of time. In effect, it would be difficult to test for their properties. In the higher grade levels, you will learn that there are ways to infer the electrical conductivities of these elements.
Electrical conductivity clearly distinguishes metals from nonmetals but there is one exception. Refer to the periodic table. Which element is electrically conductive even if it is a nonmetal?

           One form of carbon is graphite. It is commonly available as the black rod in your pencils. Get your sharpened pencil. Place the black rod in between the end tips of your improvised conductivity tester. Make sure that the black rod is in contact with the tips of the tester. What happened?

          In the higher grade levels, you will learn why carbon (graphite) though a nonmetal is electrically conductive.

          Look for other objects and test if they are made up of metal or nonmetal. Write down these objects in the appropriate box of the diagram below.

         Were you able to find a cooking pot as one of your test objects? What element is it mainly made of?
Refer to Table 2. This table shows the thermal conductivity values of some elements expressed in Watt/centimeter-Kelvin (W/cmK). Thermal conductivity is the ability of an element to allow heat to pass through it. The higher the value,