Properties of Matter: Argon (Ar)

General Properties

Protons: 18 Atomic Number: 18

Neutrons: Approximately 22 Atomic Mass: 39.95

Electrons:18 Family: 18 - Noble Gases

Valence Shell Electrons: 8 (full outer shell) Period: 3

Toxicity

Toxicity is how toxic an element is, which basically is how poisonous it is.

Argon, again, is completely non-toxic,

but it does not give your body oxygen,

so therefore it is an asphyxiant (it suf-

focates you), so its not good for you

either.

Reaction with Air

Some elements also react with air; a common chemical reaction being the element tarnishing. Argon, being a Noble Gas in the last family, is extremely inert and does not react with air under any circumstance.

As you can see in this photo, sodium metal is silver in appearance when first cut but quickly tarnishes to become the dull brown you can see on the outside of the block of metal.

Crystal Structure

Crystal structure is the 3D shape of the particles of a specific element. Each element has a different crystal structure. Some examples are cubic, hexagonal, trigonal, and orthorhombic.

Argon has a face-centered cubic

crystal structure.

Colour

Chemical Properties

Colour is considered a physical characteristic because it does not have to do with the chemical properties of a substance. Colour is determined by the types of light reflected

or absorbed by an object's surface.

Chemical properties are the characteristics that an element has that appear during a chemical reaction: when the substance's composition changes. Some examples of chemical properties include reaction with air, reaction with water, reaction with acids, ability to burn (flammability), reaction to heat, toxicity, radioactivity, etc.

For example, argon is a colourless gas, like all of the noble gases, but when placed in a high voltage electric field, it glows a bright lilac/violet.

Reaction with Water

Thermal Conductivity

Some elements have very extreme reactions when placed in water.

Argon, however, does

not react with water,

although it does dis-

solve slightly.

Thermal conductivity is basically the amount of heat that passes in a certain amount of time from one area to another certain area. When testing thermal conductivity the two different areas differ by one degree. Since heat always transfers from hotter areas to cooler areas, you can measure the amount of time it takes for the heat to move from one area to another. Thermal conductivity is measured in watts per meter kelvin, watts being energy, meters being distance, and kelvin being temperature.

Argon has a conductivity of 0.01772W m-1 K-1.

Ability to Burn (Flammability)

Caesium when added to water

State/Phase

Ability to burn is exactly what it sounds like: an elements ability to burn.

Argon isn't a good example of this, though, because it is extremely inert and will not burn under any circumstance.

The state, or phase, of an element is basically whether it is a solid, liquid, gas, or plasma at room temperature (* C). All elements can change state.

At room temperature, Argon is a gas.

Density

Density is the amount of particles that occupy a certain space. It is usually measured in

grams per cubic centimeter, or

grams per liter.

Argon is 1.784 g/L dense.

Melting/Boiling Point

Every element has a melting point and a boiling point. The melting point is when the element as a solid begins to melt into a liquid, and the boiling point is when the element as a liquid begins to evaporate into a gas.

Argon's melting point is -189.36* C/83.79 K, and its boiling point is -185.85*C/87.3 K.

Physical Characteristics

A physical characteristic is a property that can be used to identify matter and that describes a substance's appearance or state. Some examples of physical characteristics include colour, lustre (shininess), melting/boiling point, hardness, malleability (ability to be shaped into sheets), crystal shape, etc. Not all physical characteristics apply to every element; for example, you can't say what the lustre of a gas is, or what it's malleability is.

State/Phase

Colour

Solubility

Crystal Structure

Properties of Matter: Argon (Ar)