The periodic table organizes elements in a way that reveals patterns in their properties. This lesson follows the development of that organization, from early attempts to group similar elements to the modern table based on atomic number.
As chemists discovered and purified more elements, they noticed that some elements behaved alike. Lithium, sodium, and potassium, for example, are shiny metals that conduct heat and electricity well and share chemical properties. Calcium, strontium, and barium share some characteristics with one another, but their chemistry differs from that of lithium, sodium, and potassium. Fluorine, chlorine, bromine, and iodine form another group with shared properties.
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What is the periodic law?
The periodic law states that the properties of elements are periodic functions of their atomic numbers. When elements are ordered by atomic number, patterns in their properties recur.
What is a group in the periodic table?
A group is a vertical column in the periodic table. Elements in the same group generally share similar properties.
What is a period in the periodic table?
A period is a horizontal row in the periodic table. The modern table has seven periods.
How is the modern periodic table ordered?
It arranges elements in increasing order of atomic number, rather than increasing order of atomic mass.
How do metals typically behave and appear?
Metals are generally shiny, malleable, and ductile, and they conduct heat and electricity well.
Quiz questions
What did Mendeleev and Meyer use to arrange the elements in their early tables?Answer: They arranged the known elements in order of increasing atomic mass.
What key feature distinguished Mendeleev's work from Meyer's table?Answer: Mendeleev left gaps and used the table to predict the existence and properties of undiscovered elements.
What is the modern periodic law?Answer: The properties of elements are periodic functions of their atomic numbers.
In the modern periodic table, what do elements in the same vertical column generally have in common?Answer: They tend to have similar properties.
Which description best fits a metalloid?Answer: It has some properties of metals and some properties of nonmetals, and conducts heat and electricity moderately well.
Based on Chemistry 2e by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.