Using the Periodic Table
Using the Periodic Table: Chapter 10, Lesson 1
Overview of the Periodic Table
The periodic table organizes all known elements in a structured way.
Arrangements of elements are key for understanding relationships among them.
No specific shape is mandated for the periodic table, but the relationship of elements is significant.
Comparison to a grocery store: elements are systematically arranged, making it more accessible to locate and understand.
Importance of Structure
A chaotic arrangement (like a junk drawer) leads to inefficiency.
Just as stores categorize items (dairy, canned goods, produce), the periodic table categorizes elements.
The organization allows for easier access to information about the elements.
Historical Background
Dmitry Mendeleev (1869) developed the first periodic table.
Key features:
Arranged elements by increasing atomic mass.
Noted patterns in physical and chemical properties.
Predictions made for undiscovered elements based on gaps.
Example: Predicting properties of undiscovered elements in gaps.
Key Terms
Periodic: Indicates repeating patterns in properties of elements based on their position.
Atomic mass: The mass of an atom, used initially by Mendeleev for organization.
Atomic number: Number of protons in an element (later used by Henry Moseley for more accurate arrangement).
Mendeleev's Contributions
Mendeleev’s organization led to important predictions:
Elements in the same column have similar properties.
Example of tellurium and iodine’s placement due to property similarities rather than atomic mass.
Transition to Modern Table
Henry Moseley resolved inconsistencies by organizing the periodic table by atomic number rather than atomic mass.
This organization provided a clearer understanding of element relationships and corrected earlier arrangement issues.
Modern Periodic Table Features
Organized into columns (groups) and rows (periods).
Groups (columns) represent elements with similar chemical properties and reactivity.
Modern tables provide additional information such as:
Element name, symbol, atomic number, atomic mass, and state of matter (solid, liquid, gas).
Group examples:
Noble gases: Group 18.
Alkaline Earth Metals: Group 2.
Halogens: Group 17.
Properties of Metals, Nonmetals, and Metalloids
Metals:
Located on the left side of the periodic table.
Characteristics include: metallic luster, malleability, ductility, and conductivity.
Nonmetals:
Located on the right side.
Properties include: lack of luster, poor conductivity, and brittleness.
Many are gases at room temperature.
Metalloids:
Found between metals and nonmetals; possess properties of both.
Practical Use of Periodic Table
Used for understanding properties of known elements and predicting those of new ones.
The periodic table aids in research and study of chemistry by categorizing and relating various elements.
Example: Scientists hypothesize about properties of new element 119 based on its predicted position in Group 1.
Notable Scientists
Dmitry Mendeleev: Creator of the first periodic table.
Henry Moseley: Improved the arrangement by atomic number.
Glenn Seaborg: Key figure in modern periodic table layout, particularly for actinides and lanthanides.
Notably, Seaborg is the only person to have an element (Seaborgium) him while alive.
Summary
The periodic table is an essential tool in chemistry, illustrating relationships between elements based on physical and chemical properties. It serves as a predictive model for future discoveries in the field of chemistry, continuously evolving as new elements are synthesized and integrated into the established framework.