Chemistry - Periodic Table Trends
Periodic patterns become apparent when the periodic table is closely examined, focusing on
various chemical and physical properties. This brief overview is designed to explain these
properties and the trends observed in the table.
Valence Electrons
Valence electrons are the electrons located in the outermost shells of an atom. These electrons
are crucial because they are the only ones involved in forming chemical bonds:
Across a period: Increases
Down a group: Remains constant
Metallic Character
Metallic character refers to traits commonly found in metals, such as shininess, electrical
conductivity, ductility (the ability to be drawn into thin wires), and malleability (the ability to be
hammered into thin sheets). Metalloids, positioned along the zig-zag line on the periodic table,
can exhibit properties of both metals and nonmetals.
Across a period: Decreases
Down a group: Increases
Atomic Radius
The atomic radius is the distance from the nucleus's center to the outer boundary of the electron
cloud.
Across a period: The atomic radius decreases because the nuclear charge increases,
pulling the electrons closer to the nucleus and making the atom smaller.
Down a group: The atomic radius increases due to the addition of energy levels, which
enlarges the atom.
Ionic Radius
The ionic radius measures the distance between the nucleus and the outermost electrons in an
ion. It's important to note that ionic radius is not a periodic trend.
Cations: These are positive ions formed by metals and are smaller than their neutral
atoms because losing an electron increases the nuclear charge.
Anions: These are negative ions formed by nonmetals and are larger than their neutral
atoms because gaining an electron decreases the nuclear charge, reducing the inward pull.
Periodic patterns become apparent when the periodic table is closely examined, focusing on
various chemical and physical properties. This brief overview is designed to explain these
properties and the trends observed in the table.
Valence Electrons
Valence electrons are the electrons located in the outermost shells of an atom. These electrons
are crucial because they are the only ones involved in forming chemical bonds:
Across a period: Increases
Down a group: Remains constant
Metallic Character
Metallic character refers to traits commonly found in metals, such as shininess, electrical
conductivity, ductility (the ability to be drawn into thin wires), and malleability (the ability to be
hammered into thin sheets). Metalloids, positioned along the zig-zag line on the periodic table,
can exhibit properties of both metals and nonmetals.
Across a period: Decreases
Down a group: Increases
Atomic Radius
The atomic radius is the distance from the nucleus's center to the outer boundary of the electron
cloud.
Across a period: The atomic radius decreases because the nuclear charge increases,
pulling the electrons closer to the nucleus and making the atom smaller.
Down a group: The atomic radius increases due to the addition of energy levels, which
enlarges the atom.
Ionic Radius
The ionic radius measures the distance between the nucleus and the outermost electrons in an
ion. It's important to note that ionic radius is not a periodic trend.
Cations: These are positive ions formed by metals and are smaller than their neutral
atoms because losing an electron increases the nuclear charge.
Anions: These are negative ions formed by nonmetals and are larger than their neutral
atoms because gaining an electron decreases the nuclear charge, reducing the inward pull.
