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Metals

Introduces properties of the largest group of elements.

You are watching: Are non metals good conductors of heat

· Identify the metals class ofelements.

· Describe properties of metals.

· Explain why metals are good conductors of electricity.

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When you think of metals, do you think of solid objects such as iron nails and gold jewelry? If so, it might surprise you to learn that the shiny liquid pouring out of the pipette in the photo above is also a metal. It’s called mercury, and it’s the only metal that normally exists on Earth as a liquid. Just what are metals, and what are their properties? Read on to find out.

What Are Metals?

Metalsareelementsthat can conduct electricity. They are one of three classes of elements (the other two classes arenonmetalsandmetalloids). Metals are by far the largest of the three classes. In fact, most elements are metals. All of the elements on the left side and in the middle of the periodic table, except for hydrogen, are metals. There are several different types of metals, including alkali metals in group 1 of the periodic table,alkaline Earth metalsin group 2, andtransition metalsin groups 3–12. The majority of metals are transition metals.

Properties of Metals

Elementsin the same class share certain basic similarities. In addition to conducting electricity, many metals have several other shared properties, including those listed below. You can dig deeper into the properties of metals at this URL:http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/periodictable/metalsrev1.shtml.

· Metals have relatively highmeltingpoints. This explains why all metals except for mercury aresolidsat roomtemperature.

· Most metals are good conductors ofheat. That’s why metals such as iron, copper, and aluminum are used for pots and pans.

· Metals are generally shiny. This is because they reflect much of the light that strikes them. The mercury pictured above is very shiny.

· The majority of metals are ductile. This means that they can be pulled into long, thin shapes, like the aluminum electric wires pictured in theFigurebelow.

· Metals tend to be malleable. This means that they can be formed into thin sheets without breaking. An example is aluminum foil, also pictured in theFigurebelow.

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Q:The defining characteristic of metals is their ability to conduct electricity. Why do you think metals have this property?

A:The properties of metals—as well as of elements in the other classes—depend mainly on the number and arrangement of theirelectrons.

Explaining the Properties of Metals

To understand why metals can conduct electricity, consider the metal lithium as an example. An atom of lithium is modeled below. Look at lithium’selectrons. There are two electrons at the firstenergy level. This energy level can hold only two electrons, so it is full in lithium. The second energy level is another story. It can hold a maximum of eight electrons, but in lithium it has just one. A full outer energy level is the most stable arrangement of electrons. Lithium would need to gain seven electrons to fill its outer energy level and make it stable. It’s far easier for lithium to give up its one electron in energy level 2, leaving it with a full outer energy level (now level 1). Electricity is a flow of electrons. Because lithium (like most other metals) easily gives up its “extra” electron, it is a good conductor of electricity. This tendency to give up electrons also explains other properties of metals such as lithium.

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Summary

· Metals are elements that can conduct electricity. Most elements are metals.

· All metals except for mercury aresolidsat roomtemperature. Many metals are shiny, ductile, and malleable. Most are also good conductors ofheat.

· Electricity is a flow ofelectrons.Atomsof metals tend to give up electrons, explaining why they are good conductors of electricity. The tendency to give up electrons also explains many of the other properties of metals.

Explore More

At the following URL, click on any one of the metals in the interactive periodic table. Read the information provided about your choice of metal, and then make a poster demonstrating its structures, properties, and uses.

http://www.ptable.com/

Review

1. What are metals?

2. List several properties of metals.

3. Explain why metals can conduct electricity

Nonmetals

Introduces properties of the second largest group of elements.

· Identify the nonmetals class ofelements.

· List properties of nonmetals.

· Explain why nonmetals vary in their reactivity and cannot conduct electricity.

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The three puresubstancespictured above have the distinction of being among the top tenelementsthat make up the human body. All three of them belong to the class of elements called nonmetals. Most of the elements that comprise the human body—as well as the majority of other living things—are nonmetals. In fact, seven of the top ten elements in your own body belong to this class of elements. What do you know about nonmetals? What are their properties, and how are they different from other elements? In this article, you’ll find out.

What Are Nonmetals?

Nonmetalsareelementsthat generally do not conduct electricity. They are one of three classes of elements (the other two classes aremetalsandmetalloids.) Nonmetals are the second largest of the three classes after metals. They are the elements located on the right side of the periodic table.

Q:From left to right across each period (row) of the periodic table, each element hasatomswith one more proton and one more electron than the element before it. How might this be related to the properties of nonmetals?

A:Because nonmetals are on the right side of the periodic table, they have moreelectronsin their outerenergy levelthan elements on the left side or in the middle of the periodic table. The number of electrons in the outer energy level of an atom determines many of its properties.

Properties of Nonmetals

As their name suggests, nonmetals generally have properties that are very different from the properties ofmetals. Properties of nonmetals include a relatively lowboilingpoint, which explains why many of them aregasesat roomtemperature. However, some nonmetals aresolidsat room temperature, including the three pictured above, and one nonmetal—bromine—is a liquid at room temperature. Other properties of nonmetals are illustrated and described in theTablebelow.

Two Properties of Nonmetals

Illustration

Property

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Most nonmetals are poor conductors ofheat. In fact, they are such poor conductors of heat that they are often used for insulation. For example, the down filling in this sleeping bag is full of air, which consists primarily of the nonmetalgasesoxygen and nitrogen. These gases prevent body heat from escaping to the cold outside air.

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Solid nonmetals are generally dull and brittle like these pieces of iodine. Like other nonmetals, iodine lacks the luster ofmetalsand will easily crack and crumble.

Reactivity of Nonmetals

Reactivity is how likely an element is to react chemically with other elements. Some nonmetals are extremely reactive, whereas others are completely nonreactive. What explains this variation in nonmetals? The answer is their number of valenceelectrons. These are the electrons in the outerenergy levelof an atom that are involved in interactions with otheratoms. Let’s look at two examples of nonmetals, fluorine and neon. Simple atomic models of these two elements are shown in theFigurebelow.

Q:Which element, fluorine or neon, do you predict is more reactive?

A:Fluorine is more reactive than neon. That’s because it has seven of eight possibleelectronsin its outerenergy level, whereas neon already has eight electrons in this energy level.

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Although neon has just one more electron than fluorine in its outer energy level, that one electron makes a huge difference. Fluorine needs one more electron to fill its outer energy level in order to have the most stable arrangement of electrons. Therefore, fluorine readily accepts an electron from any element that is equally “eager” to give one up, such as the metal lithium or sodium. As a result, fluorine is highly reactive. In fact, reactions with fluorine are often explosive, as you can see in the URL below. Neon, on the other hand, already has a full outer energy level. It is already very stable and never reacts with other elements. It neither accepts nor gives up electrons. Neon doesn’t even react with fluorine, which reacts with all other elements except helium.

http://www.youtube.com/watch?v=vtWp45Eewtw(6:42)

Why Most Nonmetals Cannot Conduct Electricity

Like most other nonmetals, fluorine cannot conduct electricity, and its electrons explain this as well. Anelectric currentis a flow of electrons. Elements that readily give up electrons (the metals) can carry electric current because their electrons can flow freely. Elements that gain electrons instead of giving them up cannot carry electric current. They hold onto their electrons so they cannot flow.

Summary

· Nonmetals are elements that generally cannot conduct electricity. They are the second largest class of elements after metals. Examples of nonmetals include hydrogen, carbon, chlorine, and helium.

· Properties of nonmetals include a relatively lowboilingpoint, so many nonmetals aregases. Nonmetals are also poor conductors ofheat, and solid nonmetals are dull and brittle.

· Some nonmetals are very reactive, whereas others are not reactive at all. It depends on the number of electrons in their outer energy level.

· Reactive nonmetals tend to gain electrons. This explains why they cannot conduct electricity, which is a flow of electrons.

Explore More

Watch the video about nonmetals at the following URL, and then answer the questions below.

http://www.youtube.com/watch?v=-q1OW8vJ3wA(5:16)

1. The science teacher in the video does an experiment in which he tests the reactivity of four nonmetal gases. How does he test them?

2. What is the outcome of the experiment?

3. Based on this outcome, what conclusion can you draw?

4. Why do the gases differ in reactivity?

Review

1. What are nonmetals?

2. List properties of nonmetals.

3. Explain why nonmetals vary in their reactivity.

4. Carbon cannot conduct electricity. Why not?

Metalloids

Introduces properties of the smallest group of elements.

· Identify the metalloids class ofelements.

· List physical properties of metalloids.

· Explain why some metalloids react likemetalsand others react like nonmetals.

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What is this intricate orb? It is the greatly magnified skeleton of single-celled ocean organisms call radiolarian. The skeleton is made of an element that is extremely common on Earth. In fact, it is the second most abundant element in Earth’s crust. It is also one of the most commonelementsin the entireuniverse. What is this important element? Its name is silicon, and it belongs to a class of elements called metalloids.

What Are Metalloids

Metalloidsare the smallest class ofelements. (The other two classes of elements aremetalsand nonmetals). There are just six metalloids. In addition to silicon, they include boron, germanium, arsenic, antimony, and tellurium. Metalloids fall between metals and nonmetals in the periodic table. They also fall between metals and nonmetals in terms of their properties.

Q:How does the position of an element in the periodic table influence its properties?

A:Elements are arranged in the periodic table by theiratomic number, which is the number ofprotonsin theiratoms. Atoms are neutral in electric charge, so they always have the same number ofelectronsas protons. It is the number of electrons in the outerenergy levelof atoms that determines most of the properties of elements.

Chemical Properties of Metalloids

How metalloids behave in chemical interactions with other elements depends mainly on the number ofelectronsin the outerenergy levelof theiratoms. Metalloids have from three to six electrons in their outer energy level. Boron, pictured in theFigurebelow, is the only metalloid with just threeelectronsin its outerenergy level. It tends to act likemetalsby giving up its electrons inchemical reactions. Metalloids with more than four electrons in their outer energy level (arsenic, antimony, and tellurium) tend to act like nonmetals by gaining electrons in chemical reactions. Those with exactly four electrons in their outer energy level (silicon and germanium) may act like either metals or nonmetals, depending on the other elements in the reaction.

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Physical Properties of Metalloids

Most metalloids have some physical properties of metals and some physical properties of nonmetals. For example, metals are good conductors of bothheatand electricity, whereas nonmetals generally cannot conduct heat or electricity. And metalloids? They fall between metals and nonmetals in their ability to conduct heat, and if they can conduct electricity, they usually can do so only at higher temperatures. Metalloids that can conduct electricity at higher temperatures are called semiconductors. Silicon is an example of a semiconductor. It is used to make the tinyelectric circuitsin computer chips. You can see a sample of silicon and a silicon chip in theFigurebelow.

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Metalloids tend to be shiny like metals but brittle like nonmetals. Because they are brittle, they may chip like glass or crumble to a powder if struck. Other physical properties of metalloids are more variable, including theirboilingandmeltingpoints, although all metalloids exist assolidsat roomtemperature. You can learn about the properties of specific metalloids by watching the video at this URL:

http://www.youtube.com/watch?v=NO36yksPOBM(6:50)

Summary

· Metalloids are the smallest class of elements, containing just six elements. They fall between metals and nonmetals in the periodic table.

· How metalloids behave in chemical interactions with other elements depends mainly on the number of electrons in the outer energy level of theiratoms. Metalloids may act either like metals or nonmetals inchemical reactions.

· Most metalloids have some physical properties of metals and some physical properties of nonmetals. They fall between metals and nonmetals in their ability to conductheatand electricity. They are shiny like metals but brittle like nonmetals. All exist assolidsat roomtemperature.

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Explore More

Because metalloids are similar in some ways to metals and in other ways to nonmetals, to understand metalloids you need to know about these other two classes of elements. Watch the following video on classes of elements. Then, using information from the video, make a table comparing and contrasting metals, nonmetals, and metalloids.