3.6 The Periodic Table

The Periodic Law states that the properties of elements are periodic functions of their atomic numbers. This means that when elements are arranged in order of increasing atomic number, elements with similar chemical and physical properties recur at regular intervals or periods.

In the periodic table, elements are organized into rows (periods) and columns (groups or families):

• Periods (horizontal rows): Elements in the same period have the same number of electron shells but different numbers of electrons in those shells. Properties gradually change across a period.

  • left to right: Increasing atomic number

• Groups (vertical columns): Elements in the same group have similar chemical properties because they have the same number of valence electrons, which determines their reactivity and bonding behavior. For example, Group 1 elements are all alkali metals and are highly reactive.

  • top to bottom: Increasing number of shells

Metals (Located on the left and center of the periodic table)

• • Physical Properties:

    • • Solid at room temperature (except mercury, which is liquid).

      • Shiny, metallic luster with good reflectivity.

      • Malleable and ductile; can be shaped and drawn into wires.

      • Excellent conductors of heat and electricity.

      • High density and generally high melting and boiling points.

  • Chemical Properties:

    • • Tend to lose electrons easily, forming cations (+ ions) in reactions.

      • Reactivity varies widely (e.g., alkali metals are highly reactive, while transition metals are less so).

      • Often form ionic compounds with nonmetals (e.g., iron oxide) and metallic bonds with other metals.

  • Uses: Structural materials (e.g., iron, aluminum), electrical wiring (e.g., copper), jewelry and coins (e.g., gold, silver), and catalysts (e.g., platinum in catalytic converters).

Group 1: Alkali Metals

• Physical Properties: Soft, silvery metals with low density and low melting points.

• Chemical Properties: Extremely reactive, especially with water; react to form +1 ions. Stored under oil to prevent reaction with air or moisture.

• Uses: Sodium and potassium are essential in biological systems; lithium is used in batteries.

Group 2: Alkaline Earth Metals

• • Physical Properties: Harder and denser than alkali metals, shiny, with relatively high melting points.

  • Chemical Properties: Reactive, though less so than alkali metals; form +2 ions. Often found in mineral compounds.

  • Uses: Magnesium is used in lightweight alloys; calcium is essential for bones and used in cement and chalk.

Transition Metals (Groups 3-12)

• • Location: Found in the center of the periodic table, between Groups 2 and 13.

  • Physical Properties:

    • • Dense, strong, and durable.

      • Typically have high melting and boiling points.

      • Shiny, metallic luster.

      • Good conductors of heat and electricity.

      • Malleable and ductile.

  • Chemical Properties:

    • • Less reactive than alkali and alkaline earth metals.

      • Can form multiple oxidation states, which gives them the ability to form a variety of compounds (e.g., iron can form +2 or +3 ions).

      • Often form colorful compounds.

      • Tend to lose electrons to form cations (positive ions), but can also participate in covalent bonding.

  • Uses:

    • • Commonly used in construction, manufacturing, and electronics (e.g., iron, copper, and titanium).

      • Act as catalysts in chemical reactions (e.g., platinum in catalytic converters).

      • Important in forming alloys (e.g., stainless steel, bronze).

Nonmetals (Located on the right side of the periodic table, plus hydrogen)

• Physical Properties:

  • • Can be gases (e.g., oxygen, nitrogen), liquids (e.g., bromine), or brittle solids (e.g., sulfur, carbon) at room temperature.

    • Poor conductors of heat and electricity.

    • Lack metallic luster, often dull in appearance (except carbon in diamond form).

• Chemical Properties:

  • • Highly reactive with metals, forming ionic compounds (e.g., sodium chloride).

    • Form covalent bonds with other nonmetals to create molecules (e.g., H₂O, CO₂).

• Uses: Essential in biological systems (e.g., oxygen, carbon), industrial chemicals (e.g., sulfuric acid), and non-metal-based compounds in a wide range of applications.

Group 17: Halogens

• • Physical Properties: Nonmetals that exist in different states at room temperature (e.g., fluorine and chlorine are gases, bromine is a liquid, iodine is a solid).

  • Chemical Properties: Very reactive, especially with alkali and alkaline earth metals to form salts; form -1 ions.

  • Uses: Chlorine is used in water purification; iodine is essential in the diet for thyroid health; fluorine is added to toothpaste for dental health.

Group 18: Noble Gases

• • Physical Properties: Colorless, odorless gases with low boiling points and densities.

  • Chemical Properties: Very unreactive (inert) due to having a full outer electron shell; rarely form compounds.

  • Uses: Helium is used in balloons and as a cooling medium; neon is used in signage; argon is used as a protective atmosphere in welding.

Metalloids (Located along the staircase line, e.g., B, Si, Ge, As, Sb, Te, and Po)

• Physical Properties:

  • • Appear metallic but are brittle and not as malleable as metals.

    • Semiconductors of electricity (conductivity can vary with temperature).

    • Often have a mix of metallic and nonmetallic luster.

• Chemical Properties:

  • • Reactivity varies depending on the element and the substance they react with.

    • Can behave as either metals or nonmetals in chemical reactions.

• Uses: Primarily in electronics (e.g., silicon in semiconductors), alloys, and glass production.

1. 1. This element is a good conductor of electricity, is shiny, and is highly ductile. It is commonly used in electrical wiring.

   2. This element exists as a gas at room temperature and makes up about 21% of Earth's atmosphere. It is essential for life.

   3. This element is brittle when solid, used in the semiconductor industry, and can conduct electricity under certain conditions.

   4. This element is a soft, highly reactive metal and is stored under oil to prevent it from reacting with air. It is commonly used in batteries.

   5. This element is a gas at room temperature, is colorless, and chemically inert, making it useful in filling balloons.

   6. This element is shiny, dense, and commonly used in jewelry and coins. It is known for its resistance to corrosion.

   7. Solid, dense, has the highest melting point of any metal, and is used in light bulb filaments and cutting tools.

   8. This element is a gas that is toxic to most living organisms, has a distinctive, pungent odor, and is commonly used in bleach and disinfectants.

   9. A lightweight, silvery metal that reacts with water (slowly with cold water, more vigorously with hot water) to release hydrogen gas. It is commonly used in strong, lightweight alloys, fireworks, and flares, and is essential for biological processes in living organisms.

   10. This element is solid, brittle, and can form a wide range of covalent compounds. It is a key component of all living organisms.

   11. Extremely dense, bluish-gray metal, used in fountain pen tips, electrical contacts, and as a hardening alloy.

   12. Lightweight, silvery-white metal, resistant to corrosion; commonly used in packaging, construction, and aerospace industries.

   13. Strong, malleable, and abundant metal; used in construction, tools, and steel production.

   14. Yellow, brittle solid; used in fertilizers, gunpowder, and vulcanizing rubber.

   15. Heavy, radioactive metal used as fuel in nuclear reactors and for military applications.

   16. Soft, silvery metal essential for bones and teeth; used in cement and to remove impurities in steelmaking.

   17. Liquid metal at room temperature; used in thermometers, barometers, and fluorescent lighting.

   18. Bluish-white metal used in galvanizing steel, making alloys, and in batteries.

   19. Nonmetal that exists in different forms; essential for life, used in fertilizers and matches.

   20. Reddish-brown liquid at room temperature; used in flame retardants and water treatment.