The elements in group 2 the second column form compounds consisting of one atom of the element and two atoms of hydrogen: These are called alkaline earth metals , with similar properties among members of that group. Other groups with specific names are the pnictogens group 15 , chalcogens group 16 , halogens group 17 , and the noble gases group 18, also known as inert gases. The groups can also be referred to by the first element of the group: For example, the chalcogens can be called the oxygen group or oxygen family.
Hydrogen is a unique, nonmetallic element with properties similar to both group 1 and group 17 elements. For that reason, hydrogen may be shown at the top of both groups, or by itself. Figure 3. The periodic table organizes elements with similar properties into groups. Atoms of each of the following elements are essential for life. Give the group name for the following elements:. In studying the periodic table, you might have noticed something about the atomic masses of some of the elements.
Element 43 technetium , element 61 promethium , and most of the elements with atomic number 84 polonium and higher have their atomic mass given in square brackets. This is done for elements that consist entirely of unstable, radioactive isotopes you will learn more about radioactivity in the nuclear chemistry module.
An average atomic weight cannot be determined for these elements because their radioisotopes may vary significantly in relative abundance, depending on the source, or may not even exist in nature. The number in square brackets is the atomic mass number and approximate atomic mass of the most stable isotope of that element. The discovery of the periodic recurrence of similar properties among the elements led to the formulation of the periodic table, in which the elements are arranged in order of increasing atomic number in rows known as periods and columns known as groups.
Elements in the same group of the periodic table have similar chemical properties. Elements can be classified as metals, metalloids, and nonmetals, or as a main-group elements, transition metals, and inner transition metals.
Groups are numbered 1—18 from left to right. The elements in group 1 are known as the alkali metals; those in group 2 are the alkaline earth metals; those in 15 are the pnictogens; those in 16 are the chalcogens; those in 17 are the halogens; and those in 18 are the noble gases. Skip to main content. They are also extremely reactive and will burst into flame or even explode on contact with water, so chemists store them in oils or inert gases. Hydrogen, with its single electron, also lives in Group 1, but the gas is considered a nonmetal.
Alkaline-earth metals: The alkaline-earth metals make up Group 2 of the periodic table, from beryllium Be through radium Ra. Each of these elements has two electrons in its outermost energy level, which makes the alkaline earths reactive enough that they're rarely found alone in nature. But they're not as reactive as the alkali metals. Their chemical reactions typically occur more slowly and produce less heat compared to the alkali metals.
Lanthanides: The third group is much too long to fit into the third column, so it is broken out and flipped sideways to become the top row of the island that floats at the bottom of the table. This is the lanthanides, elements 57 through 71 — lanthanum La to lutetium Lu. The elements in this group have a silvery white color and tarnish on contact with air.
Actinides: The actinides line the bottom row of the island and comprise elements 89, actinium Ac , through , lawrencium Lr.
Of these elements, only thorium Th and uranium U occur naturally on Earth in substantial amounts. All are radioactive. The actinides and the lanthanides together form a group called the inner transition metals.
Transition metals: Returning to the main body of the table, the remainder of Groups 3 through 12 represent the rest of the transition metals. Hard but malleable, shiny, and possessing good conductivity, these elements are what you typically think of when you hear the word metal. Many of the greatest hits of the metal world — including gold, silver, iron and platinum — live here.
Post-transition metals: Ahead of the jump into the nonmetal world, shared characteristics aren't neatly divided along vertical group lines. We can sort the elements into large classes with common properties: metals elements that are shiny, malleable, good conductors of heat and electricity—shaded yellow ; nonmetals elements that appear dull, poor conductors of heat and electricity—shaded green ; and metalloids elements that conduct heat and electricity moderately well, and possess some properties of metals and some properties of nonmetals—shaded purple.
The elements can be subdivided further by more specific properties, such as the composition of the compounds they form. For example, the elements in group 1 the first column form compounds that consist of one atom of the element and one atom of hydrogen. These elements except hydrogen are known as alkali metals , and they all have similar chemical properties. The elements in group 2 the second column form compounds consisting of one atom of the element and two atoms of hydrogen: These are called alkaline earth metals , with similar properties among members of that group.
Other groups with specific names are the pnictogens group 15 , chalcogens group 16 , halogens group 17 , and the noble gases group 18, also known as inert gases. The groups can also be referred to by the first element of the group: For example, the chalcogens can be called the oxygen group or oxygen family. Hydrogen is a unique, nonmetallic element with properties similar to both group 1 and group 17 elements.
For that reason, hydrogen may be shown at the top of both groups, or by itself. Atoms of each of the following elements are essential for life. Give the group name for the following elements:. In studying the periodic table, you might have noticed something about the atomic masses of some of the elements. Element 43 technetium , element 61 promethium , and most of the elements with atomic number 84 polonium and higher have their atomic mass given in square brackets.
This is done for elements that consist entirely of unstable, radioactive isotopes you will learn more about radioactivity in the nuclear chemistry chapter.
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