The Periodic Table
Describe the organisation of the periodic table into periods and groups, explain the contribution of Mendeleev, and use the table to identify metals, non-metals, and predict patterns in reactivity
What a learner can do afterwards
- Explains why the periodic table is arranged into periods (rows) and groups (columns)
- States that elements in the same group have similar chemical properties
- Locates metals, non-metals, and metalloids in the periodic table
- Explains how Mendeleev ordered elements by atomic weight and predicted missing elements
The lesson
You already know that everything is built from atoms and elements. Scientists took every known element and put it on one chart called the periodic table. The chart has rows called periods and columns called groups.
In 1869, a chemist named Dmitri Mendeleev lined up all the known elements in order of their atomic weight. A pattern of properties kept repeating. When an element seemed to be missing from the pattern, he left a blank space instead of forcing a bad fit, and he predicted what that missing element would be like. Years later, chemists found those exact elements, and his predictions matched.
Use where an element sits to guess what it is. Most of the table, the left and the middle, is metal. Non-metals crowd the top right corner. A jagged staircase line runs between them, and elements touching that line are metalloids, part metal and part non-metal.
Periods are rows, groups are columns, elements in the same group behave alike, and that pattern is exactly what let Mendeleev predict elements before anyone found them.
Watch it
Where it sits
Learn first
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.