2.1: periodic table groups

Periodic Table Structure Element Groups (Families) Hydrogen is unique, sitting atop Group 1 but not considered a member. Characteristics of Hydrogen:

  • State: Gas at room temperature.

  • Atomic Structure: 1 proton, 1 electron.

  • Valence Shell: Needs 2 electrons for stability.

Alkali Metals (Group 1) Properties

  • Positioned in the first column of the periodic table.

  • 1 valence electron contributes to reactivity.

Physical Characteristics:

  • Shiny

  • clay-like consistency; can be cut with a knife.

  • Most reactive metals that never occur freely in nature; always bonded with other elements.

Reaction with Water:

  • React violently, producing hydrogen gas.

Chemical Properties of Alkali Metals Losing Electrons

  • Forms M1+ ions; characterized by high metallicity and strong reducibility.

  • Hydroxides (MOH) are strong bases.

Trends

  • Atomic radius increases down the group.

  • Nuclear attraction to outermost electrons decreases.

Reactivity with Oxygen

  • Reacts to form metal oxides, leading to tarnish:

    • Lithium: Slow tarnish.

    • Sodium: Quick tarnish.

    • Potassium: Very quick tarnish.

Physical Properties of Alkali Metals Characteristics

  • Low density and melting/boiling points.

  • Good electrical and thermal conductivity.

  • Softness increases and hardness decreases down the group.

Examples in Daily Life

  • Table salt (sodium chloride).

  • Cleaning products.

  • Batteries (lithium).

  • Street lamps (sodium).

  • Fireworks (potassium).

Alkaline Earth Metals (Group 2) Overview

  • Harder and less reactive than alkali metals.

  • Two valence electrons; often form basic solutions.

Significant Elements

  • Magnesium: Essential in biological roles and used in alloys.

  • Calcium: Important for bones and manufacturing.

Transition Metals Overview

  • Includes familiar metals such as iron, copper, and silver.

  • Good conductors of heat and electricity; can lose 1 or 2 valence electrons.

Applications

  • Various industrial uses and brightly colored compounds.

  • Used in renewable energy setups (batteries).

Boron Family Characteristics

  • Atoms have 3 valence electrons; includes metal (Al) and metalloid (B).

  • Boron compounds widely used in agriculture and industry.

Carbon Family Overview

  • 4 valence electrons; contains non-metals, metalloids, and metals.

  • Carbon is fundamental to organic chemistry; crucial for life.

  • Silicon: Important for solar energy and the computing industry (semiconductors).

Nitrogen Family (Group 15) Composition

  • 5 valence electrons; includes non-metals and metals.

  • Nitrogen: Comprises 78% of the atmosphere.

Oxygen Family (Group 16) Characteristics

  • 6 valence electrons; vital for life (20% of the atmosphere).

  • Oxygen is the most abundant element in the earth's crust.

Halogen Family (Group 17) Properties

  • 7 valence electrons; highly reactive non-metals; never found free in nature.

Reactivity Trends

  • Reacts with alkali metals to form salts.

  • Color deepens and density increases from top to bottom of the group.

Noble Gases (Group 18) Characteristics

  • Colorless and unreactive due to full outer electron shells.

  • Includes helium, neon, argon, etc.; present in small atmospheric amounts.

Rare Earth Elements Classification

  • Encompass lanthanide and actinide series; many are synthetic.

Industrial Uses

  • Strong affinity for sulfur and oxygen; used for purifying steel.

  • Essential in fluorescent lamps and catalytic processes in petroleum refining.