Group (periodic table)

The table of bits has many columns.

These columns are called groups. Each group is like a family. The bits in a group act in a similar way. This is because they have the same outer parts.

There are 18 numbered groups. Some columns do not have numbers. Some people use old names for these groups. One group is called the oxygen group.

Groups can also be named after one bit. This helps us find them. It is a great way to sort things.

The periodic table is a chart of elements. Each column in this chart is called a group.

Groups are like families of elements. Elements in a group act in similar ways. This happens because their atoms have similar outer parts. These parts are called electron shells. The location of the outer electron helps decide how an element acts.

There are 18 numbered groups in the table. Some columns do not have numbers. These are called f-block columns. The IUPAC is a group that sets rules for science. Since 1988, they have used the 1-18 numbering system.

Groups can have special names. For example, group 16 is the oxygen group. It is also called the chalcogens. Group 17 is known as the halogens. Some groups are named after a single element. Group 11 contains metals like gold. These are sometimes called coinage metals. Some people use old ways to name groups. They used Roman numbers or letters like A and B. The new 1-18 system is now the main way to name them.

The periodic table is a map of all the elements. Each vertical column in this chart is called a group. You might also hear scientists call these groups families. This name is helpful because elements in a group act in similar ways. They share many physical or chemical characteristics. This happens because of how their atoms are built.

Groups work because of the outermost electron shells. An electron shell is the outer part of an atom. The location of the outer electron is very important. It mostly decides how an element behaves. Elements in the same column have similar outer shells. This means they have the same core charge. Because they share this trait, they act like a family.

Scientists have used different ways to name these groups. In the past, people used Roman numerals like I to VIII. They also used letters like A and B. Two older systems were the CAS and the old IUPAC. The CAS system was popular in the United States. The old IUPAC system was more common in Europe. These old systems were often confusing to use.

Today, we use a modern numbering system. There are 18 numbered groups in the table. The IUPAC has recommended this 1-18 system since 1988. There are also 14 f-block columns between groups 2 and 3. These specific columns do not have numbers. The new system numbers groups from left to right. This helps avoid the confusion of the old ways.

Groups often have special names or nicknames. Group 16 is called the oxygen group or chalcogens. Group 17 is known as the halogens. Some groups are named after a single element. For example, group 11 includes gold. These are sometimes called coinage metals. Other sets of elements are called noble metals or precious metals. These names help scientists talk about how elements act together.

In the study of chemistry, a group is a vertical column of elements in the periodic table. These columns are also frequently referred to as families. The concept of a group is essential because it organizes the elements based on shared traits. Elements within the same group exhibit similar physical and chemical characteristics. This similarity is not random. It is a direct result of how the atoms of these elements are constructed.

The reason elements act like a family lies in their atomic structure. Specifically, they share similar characteristics in their outermost electron shells. These shells are the outer layers of an atom. Most chemical properties are dominated by the orbital location of these outermost electrons. Because the elements in a group have the same core charge, they tend to behave in predictable ways. This predictable behavior allows scientists to understand how an element might react with others.

Modern chemistry uses a standardized numbering system to identify these columns. There are 18 numbered groups in the periodic table, ranging from group 1 to group 18. Between group 2 and group 3, there are 14 additional columns known as the f-block. These f-block columns are not assigned numbers in the standard 1–18 system. The modern numbering is based on each atom's s, p, and d electrons. These electrons exist beyond those found in the atoms of the preceding noble gas.

Before the current system, scientists used different and often incompatible naming schemes. One system was used by the Chemical Abstract Service, or CAS, which was popular in the United States. Another system was used by the International Union of Pure and Applied Chemistry, or IUPAC, which was more common in Europe. These older systems used Roman numerals and the letters "A" and "B." For example, the letters designated the left or right side of the table in the old IUPAC system. In the CAS system, "A" meant main group elements and "B" meant transition elements. This caused confusion because the same names often meant different things in different regions.

To fix this confusion, the IUPAC recommended the modern 1–18 numbering system. This proposal was first circulated for public comment in 1985. It was later included in the 1990 edition of the Nomenclature of Inorganic Chemistry. The current system is generally accepted by the global chemistry community. However, some small debates remain regarding the exact membership of elements 1 and 2, which are hydrogen and helium. There is also some variation in textbooks regarding the inner transition metals. Even so, the correct positioning of these metals has been known since 1948. IUPAC has endorsed this positioning twice, once in 1988 and again in 2021.

Groups are often identified by specific names or by their topmost element. For instance, group 16 is known as the oxygen group or the chalcogens. Group 17 is known as the halogens, and group 18 is known as the noble gases. Some groups have "trivial names," which are common nicknames used by scientists. Group 11 contains elements like gold and is often called the coinage metals. There is some debate about whether the element roentgenium belongs in this group. While it is in group 11, it is extremely radioactive and short-lived. This makes it difficult to use for actual coinage.

Beyond the vertical columns, scientists sometimes use the word "group" to describe other sets. These sets are not defined by being a column in the periodic table. Examples include the noble metals, precious metals, and refractory metals. There is also a specific term called the "iron group." In a general chemistry context, this usually refers to group 8. However, it can also refer to a specific set containing iron, cobalt, and nickel. In the fields of astrophysics and nuclear physics, the term has a different meaning. In those sciences, the iron group refers to iron, cobalt, nickel, chromium, and manganese.