The Periodic Table: Arrangement, Groups, and Element Properties

Chemistry Fundamentals

Arranging the Elements: The Periodic Table

• Organizing the elements according to their properties.
• Dmitri Mendeleev discovered a pattern to the elements in 1869.
• Periodic means “happening at regular intervals.”
• Mendeleev found that element properties follow a pattern that repeated every 7 elements.
• He found that elements yet to be found would fill the gaps. By 1886, all of the gaps had been filled.
• In 1914, Henry Moseley determined the number of protons. Elements were arranged by atomic number. The Periodic Law states that the repeating physical and chemical properties of elements change periodically with the element's atomic number.

Classifying Elements on the Periodic Table

• Metals: Found to the left of the zigzag line on the periodic table. Most metals are soft at room temperature.
• Non-Metals: Found to the right of the zigzag line on the periodic table. More than half are gases at room temperature.
• Elements are classified as metals, non-metals, and metalloids according to their properties.
• Colors and symbols help decode the periodic table.
• Each square on the periodic table includes an element's name, chemical symbol, atomic number, and atomic mass.
• Columns (up to down) are called groups, and rows (from one side to another) are called periods.

Grouping Elements by Properties

Elements whose atoms undergo such a process are called reactive and can combine to form compounds.

Group 1: Alkali Metals

They share physical and chemical properties.

• Group contains: Metals
• Electrons in outer level: 1
• Reactivity: Very Reactive
• Other shared properties: Silvery and low density

Group 2: Alkali-Earth Metals

• Group contains: Metals
• Electrons in outer level: 2
• Reactivity: Very reactive but less than Alkali Metals
• Other shared properties: Silvery color and high density

Properties of Transition Metals

Tend to be shiny and to conduct thermal energy and electric current well.

Lanthanides and Actinides

The two rows at the end (separated). Actinides are radioactive or unstable.

Group 13: Boron Group

The most common element from this group is aluminum.

Aluminum is the most abundant element in Earth's crust.

• Group contains: One metalloid and four metals
• Electrons in the outer level: 3
• Reactivity: Reactive
• Other shared properties: Solids at room temperature

Group 14: Carbon Group

The non-metal carbon can be found uncombined in nature. Carbon also forms a wide variety of compounds.

• Group contains: One non-metal and 2 metalloids
• Electrons in the outer level: 5
• Properties: Solid at room temperature (except nitrogen)

Group 15: Nitrogen Group

Nitrogen makes up about 80% of the air you breathe.

• Group contains: Two non-metals and one metal
• Electrons in the outer level: 6
• Reactivity: Reactive

Group 16: Oxygen Group

Oxygen makes up 20% of air. Oxygen is necessary for substances to burn.

• Group contains: Three non-metals, one metalloid, and one metal
• Properties: All are solid at room temperature (except oxygen)