In 1869 a Russian chemist, Dmitri Mendeleev (pictured here), produced a simple grouping of known elements. Mendeleev’s grouping of elements was later called the Periodic Table of the Elements. The table was given its name because the arrangement of the elements reflected the periodic change in their properties. Other chemists had attempted to organize the elements by their similarities, but Mendeleev’s table was the most successful. He is considered the “father” of the modern Periodic Table.

The modern Periodic Table groups elements according to their atomic structure, and more specifically according to their atomic numbers. The atomic structure of each element is determined by three factors: the number of positively charged protons found in the nucleus, the number of negatively charged electrons surrounding the nucleus, and how the electrons are arranged in orbitals. Atomic number refers to the number of protons in the nucleus of an atom (6 for carbon, 50 for tin, 79 for gold, etc.). This arrangement of elements by atomic number also results in the organization of elements according to the physical and chemical properties. The resulting relevance to this CELL is an alignment of elements into three groups: metals, nonmetals, and metalloids (see legend of the chart below).

The Periodic Table is arranged into rows (across) and columns (up and down). The table’s rows are called periods, which are numbered one through seven. In order for the rows to fit on a page, the sixth and seventh periods also include the rows at the bottom of the table. The table’s columns are called groups or families. The International Union of Pure and Applied Chemistry (IUPAC) has proposed a naming convention that numbers the groups or families from 1 through 18, from left to right.

Each group of elements has characteristic chemical and physical properties and these properties can assist in their identification. For example, the elements in Group 1 are known as the alkali metals, which easily react with water, even though hydrogen (H) the first element in the group, is not a metal. Group 17 elements are the halogens (see the periodic table above), which are also extremely reactive. Metals are often shiny or lustrous in appearance and are hard and malleable, while nonmetals are often gases or solids which are soft, brittle, and dull in appearance. Metalloids, which are select elements in Groups 13-17, can be shiny or dull in appearance and either soft or hard, malleable, or brittle.

Below is a LabLearner video that introduces the Atomic Structure CELL. Please take the time to view the video below. The most important information will be discussed again later in the CELL, simply focus on the overall concepts at this time.