period

(noun)

A horizontal row in the periodic table, which signifies the total number of electron shells in an element's atom.

Related Terms

Examples of period in the following topics:

  • Periodic Trends

  • The Periodic Table

    • In the typical periodic table, each element is listed by its element symbol and atomic number.
    • Each row of the periodic table is called a period and each column of the periodic table is called a group (or family).
    • Elements within the same period or group have similar properties.
    • The periodic table is a tabular display of all the chemical elements.
    • Identify the common periodic trends that can be deduced from the periodic table of elements

  • Periods 1 through 3

    • Elements of the same period have the same number of electron shells.
    • Electron are organized in energy levels or electron shells, which correspond to the periods on the periodic table.
    • The periodic table codifies the energy levels in periods, the rows on the table.
    • In the periodic table, there are 2 electrons in period 1, while both periods 2 and 3 have 8 electrons in the filled level.
    • Discuss the relationship between an atom's electron structure and its period (row) on the periodic table.

  • Atomic Size

    • Atomic radii generally decrease along each period (row) of the periodic table and increase down each group (column).
    • Atomic radii vary in a predictable manner across the periodic table.
    • Therefore, the size of atoms decreases as one moves across a period from left to right in the periodic table.
    • Therefore, atomic size, or radius, increases as one moves down a group in the periodic table.
    • The atomic size trends across a period and down a group ('family' in this figure) of the periodic table are shown in this figure.

  • Periodic Trends in Metallic Properties

    • Metallic properties tend to decrease across a period and increase down a periodic group.
    • Recall that in the periodic table, each row is called a period.
    • Each of the columns of the periodic table is called a group.
    • So, the metallic properties of elements tends to decrease across a period and increase down a group.
    • Families of the periodic table are often grouped by metallic properties.

  • The Bottom of the Periodic Table

    • The periodic table currently contains 7 periods, but theorists predict that two additional periods may exist.
    • In fact, this representation is predictive in that it shows chemical families (groups) and the periodicities (periods) in their correct relative positions.
    • By using the predictive properties of the periodic table, along with a growing expertise in atomic and subatomic theory, two entirely new periods were predicted.
    • On the advice of Glenn Seaborg and others, Periods 8 and 9 were added to the periodic table, comprising the g-block.
    • The periodic table with all groups and periods in place.

  • Atomic Radius

    • Atomic radii decrease from left to right across a period and increase from top to bottom along a group.
    • In chemistry, periodic trends are the tendencies of certain elemental characteristics to increase or decrease as one progresses along a row or column of the periodic table of elements.
    • The atomic radius is one such characteristic that trends across a period and down a group of the periodic table.
    • Atomic radii vary in a predictable and explicable manner across the periodic table.
    • The radius increases sharply between the noble gas at the end of each period and the alkali metal at the beginning of the next period.

  • Ionization Energy

    • The ionization energy tends to increase as one moves from left to right across a given period or up a group in the periodic table.
    • Ionization energy increases from left to right in a period and decreases from top to bottom in a group.
    • The ionization energy of an element increases as one moves across a period in the periodic table because the electrons are held tighter by the higher effective nuclear charge.
    • This video explains the periodic trends in ionization energy....periodicity.
    • The periodic table is arranged in a manner to show trends in the characteristics of the elements.

  • Electron Affinity

    • The electron affinity of the elements generally increases across a period and sometimes decreases down a group in the periodic table.
    • Although Eea varies greatly across the periodic table, some patterns emerge.
    • Eea generally increases across a period (row) in the periodic table, due to the filling of the valence shell of the atom.
    • Periodic Properties: Part 4, Ionic Charges, Ionization Energy, Electron Affinity - YouTube
    • This table shows the electron affinities in kJ/mol for the elements in the periodic table.

  • General Trends in Chemical Properties

    • In the periodic table, the elements are placed from left to right in each period in the sequence of their atomic numbers.
    • A group, or family, is a vertical column in the periodic table.
    • Electron affinity also shows a slight trend across a period: metals (the left side of a period) generally have a lower electron affinity than nonmetals (the right side of a period), with the exception of the noble gases which have an electron affinity of zero.
    • The total number of electron shells an atom has determines the period to which it belongs.
    • The periodic table can be broken into blocks, corresponding to the highest energy electrons.