Scientists use a table called the periodic (pihr ee AH dihk) table to organize elements. The periodic table is a chart of the elements arranged into rows and columns according to their physical and chemical properties. It can be used to determine the relationships among the elements.
Today’s Periodic Table
You can identify many of the properties of an element from its placement on the periodic table. The table, as shown in Figure 4, is organized into columns, rows, and blocks, which are based on certain patterns of properties.
What is on an element key?
The element key shows an element’s chemical symbol, atomic number, and atomic mass. The key also contains a symbol that shows the state of matter at room temperature. Look at the element key for helium in Figure 5. Helium is a gas at room temperature. Some versions of the periodic table give additional information, such as density, conductivity, or melting point.
Groups
A group is a column on the periodic table. Elements in the same group have similar chemical properties and react with other elements in similar ways. There are patterns in the physical properties of a group such as density, melting point, and boiling point. The groups are numbered 1–18, as shown in Figure 4.
1. Key Concept Check What can you infer about the properties of two elements in the same group?
Periods
The rows on the periodic table are called periods. The atomic number of each element increases by one as you read from left to right across each period. The physical and chemical properties of the elements also change as you move left to right across a period.
Metals, Nonmetals, and Metalloids
Almost three-fourths of the elements on the periodic table are metals. Metals are on the left side and in the middle of the table. Individual metals have some properties that differ, but all metals are shiny and conduct thermal energy and electricity.
With the exception of hydrogen, nonmetals are located on the right side of the periodic table. The properties of nonmetals differ from the properties of metals. Many nonmetals are gases, and they do not conduct thermal energy or electricity.
Between the metals and the nonmetals on the periodic table are the metalloids. Metalloids have properties of both metals and nonmetals. Figure 6 shows an example of a metal, a metalloid, and a nonmetal.
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