Question

You are given a sample of a dark, shiny solid and asked to determine whether it is the nonmetal iodine or a metallic element. What test could you do that would enable you to answer the question without destroying the sample?

Short answer

Perform a conductivity test; iodine will not conduct electricity, but a metallic element will.

Step-by-step solution

Observe Physical Properties

Begin by examining the physical properties of the sample. Iodine, being a non-metal, has distinct properties such as sublimation. Describe what you notice about the sample—its luster, color, and texture.

Perform Conductivity Test

Set up a simple conductivity test. Connect the sample to a battery and a light bulb using wires. Metals generally conduct electricity well, while iodine does not. Observe if the light bulb lights up when the circuit is complete.

Draw Conclusions

Based on the results of the conductivity test, decide whether the sample is iodine or a metallic element. If the light bulb lights up, the sample is likely a metal due to its ability to conduct electricity. If not, it is likely iodine.

Key concepts

Nonmetals

Nonmetals are a fascinating group in the periodic table, distinct from metals in many ways. These elements are often found on the right side of the periodic table and have unique characteristics.
They don't conduct electricity well, indicating their insulating qualities, with a few exceptions like carbon in the form of graphite.
Some common nonmetals include oxygen, nitrogen, sulfur, and chlorine. To identify nonmetals, you can look at their physical and chemical properties, which often differ significantly from metals. Nonmetals tend to be dull in appearance rather than shiny. They can be brittle and break or shatter when stress is applied.
Moreover, nonmetals usually have lower melting and boiling points compared to most metals. When it comes to chemical behavior, nonmetals typically form covalent bonds by sharing electrons. Iodine, for example, sublimes at room temperature, changing directly from a solid to a gas, without becoming liquid, a distinct nonmetal property.

Metals

Metals are essential to various applications for their characteristic properties. These elements are primarily found on the left and center of the periodic table.
One key trait of metals is their ability to conduct heat and electricity effectively, largely due to the free flow of electrons within their atomic structure. Aesthetically, metals are often shiny and reflective, exhibiting a characteristic metallic luster. They are generally malleable, which means they can be hammered or rolled into sheets;
ductility allows them to be drawn into wires, an essential feature for wiring in electrical applications. Some common examples of metals include iron, gold, silver, and aluminum. These elements tend to have high melting and boiling points;
they often engage in forming solid solutions or alloys, enhancing their properties for specific uses.

Conductivity Test

A conductivity test is a simple yet informative experiment that can help determine whether a sample is a metal or a nonmetal.
This test leverages the electrical conducting properties of metals as opposed to nonmetals. To execute a conductivity test:

• Assemble a simple circuit using a battery, wires, and a light bulb.
• Securely connect the sample within the circuit.
• Complete the circuit and observe whether the light bulb illuminates.

If the sample conducts electricity, closing the circuit and lighting the bulb, it demonstrates metallic properties.
Conversely, if the bulb does not light, the material is likely a nonmetal, given its lack of free-flowing electrons needed for conductivity. This straightforward test is non-destructive, allowing the sample examination without altering the sample permanently.

Physical Properties

Physical properties help differentiate one substance from another without altering its chemical composition. These properties include aspects like appearance, density, melting point, boiling point, and electrical conductivity.
They are crucial in identifying materials and understanding their practical applications. Some physical properties of substances:

• Luster: Metals typically have a shiny appearance, while nonmetals do not.
• Color: While not always definitive, it can provide clues about a substance.
• Texture: How a substance feels to touch, which ties into its structural properties.
• Conductivity: Indicates the ability to conduct heat or electricity, providing valuable information during tests like conductivity testing.
• State of Matter: At room temperature, the state (solid, liquid, or gas) can help identify certain elements or compounds.
  Iodine, for instance, sublimates, giving it a unique identification feature in contrast to metals.

Understanding these properties can be instrumental in classifying and evaluating different materials, an important skill in both chemistry and industry applications.