20 The Periodic Table
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The Periodic Table
The periodic table shows all the elements and their physical properties; it is arranged based on atomic numbers and electron configurations.
LEARNING OBJECTIVES
Identify the common periodic trends that can be deduced from the periodic table of elements.
KEY TAKEAWAYS
Key Points
- The periodic table lists all the elements with information about their atomic weights, chemical symbols, and atomic numbers.
- The arrangement of the periodic table leads us to visualize certain trends among the atoms.
- The vertical columns (groups) of the periodic table are arranged such that all its elements have the same number of valence electrons. All elements within a certain group thus share similar properties.
Key Terms
- atomic number: The number, equal to the number of protons in an atom, that determines its chemical properties. Symbol: Z.
- group: A vertical column in the periodic table which signifies the number of valence shell electrons in an element’s atom.
- period: A horizontal row in the periodic table which signifies the total number of electron shells in an element’s atom.
Element Symbols
The periodic table is structured as an 18 X 7 grid positioned above a smaller double row of elements. The periodic table only lists chemical elements, and it includes each isotope of each element within one cell. In the typical periodic table, each element is listed by its element symbol and atomic number. For example, “H” denotes hydrogen, “Li” denotes lithium, and so on. Most elements are represented by the first letter or first two letters of their English name, but there are some exceptions. Two notable exceptions include silver and mercury. The symbol for silver is “Ag” from Latin argentum, which means “gray” or “shining.” The symbol for mercury is “Hg” from the Latinized Greek hydrargyrum, which means “water-silver.” Many periodic tables include the full name of element as well and color-code the elements based on their phase at room temperature (solid, liquid, or gas).
Rows and Periods
The element symbol is almost always accompanied by other information such as atomic number and atomic weight. Atomic number describes the number of protons in one atom of that element. For example, an atom of oxygen contains 8 protons. Elements are listed in order of increasing atomic number from left to right. Each row of the periodic table is called a period and each column of the periodic table is called a group (or family). Some groups have specific names like the halogens or noble gases. Elements within the same period or group have similar properties.
Determining Chemical Properties Using the Periodic Table
Chemical properties of each element are determined by the element’s electronic configuration, particularly by its outermost valence electrons. An element’s location in the periodic table is largely dependent on its electrons; the number of valence shell electrons determines its group, and the type of orbital in whi