Classifying Elements

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Classifying Elements

• HS Physical Science

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Classifying Elements

• About ¾ of the known elements are classified as
  metals.
• Most metals are found as compounds containing
  oxygen, sulfur, or carbon.

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Native Metals

• Gold, silver, copper and platinum are called
  native metals because they are often found in the
  pure metal, and not as a compound.

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Ores

• Minerals that contain metals in either the pure
  or combined state are called ores.

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Properties of Metals

• Most metals are shiny and reflect light when they
  are polished (called LUSTER)
• Metals can be flattened, hammered, or rolled into
  sheets (called MALLEABLE)
• All metals are SOLID at room temp. (except
  mercury)
• All metals are SILVERY except copper and gold.
• Metals are good electrical CONDUCTORS

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Why are metals good conductors?

• Lets look back to the idea of the atom.
• Remember, there are three main parts to the atom.
• Protons (positive)
• Neutrons (neutral)
• Electrons (negative)

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How the atom is organized

• The atom has the protons and neutrons in the
  center (called the nucleus), with the electrons
  around the outside.

electrons
NUCLEUS
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Where do you find electrons?

• It is hard to describe their position in the
  atom.
• Scientists used to think that electrons traveled
  in fixed paths around the nucleus.
• Now scientists infer that electrons travel in
  random paths about the nucleus much like a fruit
  fly travels around a piece of ripe fruit.

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Metals

• When metal atoms are bonded together the
  electrons become delocalized, jumping from one
  atom to another. A common analogy is to say that
  the nuclei of atoms in a metal exist in a "sea of
  mobile electrons".

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• A typical electric current can be described as
  electrons moving from one place to another. This
  can easily happen in metallic substances.

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So, if ¾ of elements are metals, what is
everything else?

• Nonmetals
• Noble gases

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Nonmetals

• Examples are carbon, hydrogen, chlorine, and
  sulfur
• Have little or no luster
• Brittle (cannot be rolled into sheets)
• Poor conductors

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Noble Gases

• Another important group found in nature
• Includes helium, neon, argon, xenon, krypton, and
  radon
• Generally do not combine with other elements

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Periodic Table

• Includes information about the elements and is
  arranged to emphasize important similarities in
  their properties.
• Scientists use something called a chemical symbol
  to represent each element.
• The first letter in each symbol is always
  capitalized, if there is a second letter it is
  lowercase.

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Chemical Symbols

• At first glance, some symbols appear to have no
  relationship to their names.
• Names of elements come from their Latin or Greek
  names.
• Other elements are named for places or people.
• Chemical symbols can also be an abbreviation of
  the English name.

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Position on the Periodic Table

• The heavy zigzag line on the periodic table
  separates the metals from the nonmetals
• The metals are on the left and the nonmetals are
  on the right.

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Metalloid

• A few elements have properties of both metals and
  nonmetals.
• These elements are called metalloids.
• They are found along the heavy zigzag line of the
  periodic table.
• Metalloids are typically gray, malleable solids
  at room temp and not good conductors.
• Sometimes metalloids are called semiconductors.