18.1 Periodicity
4 min read•june 25, 2024
The organizes elements based on and . It's divided into and , with elements in the same group sharing similar properties. This arrangement helps us understand how elements relate to each other and predict their behavior.
Atomic properties like size, , and follow specific trends across the table. These trends explain why , , and have distinct characteristics. Understanding these patterns is key to grasping element behavior and chemical reactions.
Periodic Table Organization and Trends
Classification of elements in periodic table
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- Elements organized in periodic table based on atomic number increases from left to right and top to bottom
- Atomic number represents number of protons in nucleus of atom
- determines element's position in periodic table follows specific order of orbital filling: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, etc.
- in outermost shell determine chemical properties and
- Periodic table divided into (rows) and (columns)
- Period number indicates highest (n) of (1, 2, 3, etc.)
- Group number related to number of valence electrons (1, 2, 13-18)
- Elements in same group have similar electron configurations and chemical properties
- (groups 1, 2, 13-18) have characteristic valence electron configurations (ns1, ns2, ns2np1-6)
- (groups 3-12) have partially filled d-orbitals (ns2(n-1)d1-10)
- (group 18) have full outer electron shells, following the
Trends in atomic properties
- Atomic size () trends across periods and down groups
- Decreases from left to right across period due to increasing pulls electrons closer to nucleus (Li > Be > B > C)
- Increases down group due to additional electron shells moving valence electrons farther from nucleus (Li < Na < K < Rb)
- trends across periods and down groups
- First ionization energy is energy required to remove outermost electron from neutral atom
- Increases from left to right across period due to increasing effective nuclear charge and decreasing atomic size (Li < Be < B < C)
- Decreases down group due to increasing atomic size and of inner electrons (Li > Na > K > Rb)
- Reactivity trends for and
- Metals (left side of periodic table) tend to lose electrons and form , reactivity increases down group due to lower ionization energy (Li < Na < K < Rb)
- Nonmetals (right side of periodic table) tend to gain electrons and form , reactivity increases from left to right across period due to higher (N < O < F)
- trends across periods and down groups
- Increases from left to right across period due to increasing effective nuclear charge
- Decreases down group due to increasing atomic size and shielding effect
Metals vs nonmetals vs metalloids
- Metals have distinct physical and chemical properties
- Good conductors of heat and electricity due to (Cu, Ag, Au)
- can be hammered into thin sheets and can be drawn into wires due to (Al, Fe, Pb)
- High melting and boiling points due to strong metallic bonds (W, Re, Os)
- Form and in aqueous solutions (Na2O, KOH)
- Tend to lose electrons and form cations in chemical reactions (Na → Na+, Mg → Mg2+)
- Nonmetals have contrasting properties to metals
- Poor conductors of heat and electricity () due to lack of delocalized electrons (S, P, I2)
- Brittle and not malleable or ductile due to covalent or (C, Si, P)
- Lower melting and boiling points compared to metals due to weaker (O2, Cl2, Br2)
- Form and in aqueous solutions (CO2, SO3, HCl)
- Tend to gain electrons and form anions in chemical reactions (Cl + e- → Cl-, O + 2e- → O2-)
- (semi-metals) have intermediate properties
- Located along "staircase" line between metals and nonmetals in periodic table (B, Si, Ge, As)
- Exhibit properties between metals and nonmetals, can be (Si, Ge)
- Some metalloids used in electronics due to tunable conductivity (Si in computer chips, Ge in transistors)
Special groups of elements
- and : two series of elements in the periodic table
- : 15 elements from lanthanum to lutetium, characterized by filling of 4f orbitals
- : 15 elements from actinium to lawrencium, characterized by filling of 5f orbitals
- Both groups exhibit similar chemical properties within their respective series due to similar electron configurations
Key Terms to Review (97)
Acidic Oxides: Acidic oxides are a class of chemical compounds that contain oxygen and form acidic solutions when dissolved in water. These oxides are typically formed by the reaction of non-metallic elements, such as carbon, sulfur, or nitrogen, with oxygen.
Actinides: Actinides are a series of 15 metallic elements in the periodic table from actinium (Ac) to lawrencium (Lr), with atomic numbers 89 to 103. They are known for being radioactive and having significant applications in nuclear energy.
Actinides: The actinides are a group of 15 radioactive elements in the periodic table, with atomic numbers ranging from 89 (actinium) to 103 (lawrencium). These elements are characterized by the filling of the 5f electron shell and are known for their complex electronic structures and radioactive properties.
Alkali metals: Alkali metals are a group of elements in Group 1 of the periodic table, known for their high reactivity and tendency to form +1 ions. These metals include lithium, sodium, potassium, rubidium, cesium, and francium.
Alkaline earth metals: Alkaline earth metals are elements in Group 2 of the periodic table and include beryllium, magnesium, calcium, strontium, barium, and radium. They are characterized by having two electrons in their outermost energy level which they readily lose to form divalent cations.
Aluminum: Aluminum is a lightweight, silvery-white metal that is highly abundant in the Earth's crust. It is known for its high electrical and thermal conductivity, corrosion resistance, and malleability, making it a widely used material in various industries and applications.
Anions: Anions are negatively charged ions that form when an atom or molecule gains one or more electrons. They are an essential component in the formation of ionic and molecular compounds, playing a crucial role in various chemical processes and phenomena.
Arsenic: Arsenic is a metalloid element with the atomic number 33 on the periodic table. It is known for its toxic properties and has been used in various industrial and agricultural applications, as well as in some medical treatments. In the context of periodicity, arsenic's position and properties provide insights into the behavior and trends of elements within the periodic table.
Atomic Number: The atomic number is a fundamental property of an element that represents the number of protons in the nucleus of an atom. It is a unique identifier for each element and is a crucial concept in understanding the structure and behavior of atoms, as well as their placement in the periodic table.
Atomic number (Z): The atomic number (Z) is the number of protons found in the nucleus of an atom. It determines the element's identity and its position on the periodic table.
Atomic Radius: The atomic radius is the distance from the center of an atom to its outermost shell or the edge of its electron cloud. This fundamental property of atoms is closely related to their physical and chemical behavior, as it influences the interactions between atoms and their reactivity.
Basic Oxides: Basic oxides are a class of chemical compounds formed when certain metallic elements react with oxygen. They are characterized by their ability to form basic or alkaline solutions when dissolved in water, due to the release of hydroxide ions (OH-). Basic oxides are an important concept in the study of periodicity and the properties of elements.
Beryllium: Beryllium is a rare, hard, and lightweight metallic element that is classified as an alkaline earth metal. It is known for its unique properties and has various applications in industry and technology.
Bismuth: Bismuth is a post-transition metal with the atomic number 83 and symbol Bi. It is known for its low toxicity and unique properties such as high density and low thermal conductivity.
Boron: Boron is a metalloid element that is found in the periodic table, with the atomic number 5. It is a hard, brittle, and dark-colored element that is known for its unique properties and applications in various fields, including chemistry, physics, and materials science.
Bromine: Bromine is a dense, reddish-brown liquid element that is part of the halogen group on the periodic table. It is highly reactive and has a wide range of applications, particularly in the chemical industry and in the production of various compounds.
Carbon: Carbon is a fundamental element that is essential for the formation of organic compounds and the sustenance of life. It is a versatile element that can form a wide range of structures and participate in numerous chemical reactions, making it a crucial component in various fields, including chemistry, biology, and materials science.
Cations: Cations are positively charged ions that form when an atom loses one or more of its valence electrons. They are a fundamental concept in understanding ionic and molecular compounds, ionic bonding, electrolysis, and periodicity.
Chlorine: Chlorine is a highly reactive, greenish-yellow gas that is one of the five halogens in the periodic table. It is an essential element in many chemical processes and compounds, with wide-ranging applications in various industries and everyday life.
Copper: Copper is a reddish-brown metallic element that is an essential mineral for human health and has numerous applications in various industries. It is a transition metal that exhibits unique chemical properties, making it an important component in many chemical processes and technological advancements.
Covalent Bonding: Covalent bonding is a type of chemical bond that involves the sharing of one or more pairs of electrons between atoms. This type of bond is responsible for the formation of many stable molecules and is a fundamental concept in understanding the structure and properties of various substances, including those covered in the topics of 8.3 Multiple Bonds, 18.1 Periodicity, 18.3 Structure and General Properties of the Metalloids, 18.5 Occurrence, Preparation, and Compounds of Hydrogen, and 18.7 Occurrence, Preparation, and Properties of Nitrogen.
D-orbital: The d-orbital is a type of atomic orbital found in elements with partially filled 3d electron shells. These orbitals play a crucial role in the periodic trends and chemical properties of transition metals and other elements with partially filled d-subshells.
Delocalized Electrons: Delocalized electrons are electrons in a molecule or solid that are not associated with a specific atom or bond, but are free to move throughout the entire structure. This phenomenon is particularly important in the context of periodicity, as it contributes to the unique properties and behaviors of certain elements and compounds.
Ductile: Ductility is a material property that describes the ability of a solid material to be drawn into a wire without fracturing. Ductile materials can be stretched, bent, or hammered into different shapes without losing their structural integrity.
Effective Nuclear Charge: The effective nuclear charge is the net positive charge experienced by an electron in an atom, taking into account the shielding effect of the other electrons present. It is a crucial concept in understanding the periodic trends and properties of elements.
Effective nuclear charge, Zeff: Effective nuclear charge, $Z_{eff}$, is the net positive charge experienced by an electron in a multi-electron atom. It accounts for both the actual nuclear charge and the shielding caused by other electrons.
Electron affinity: Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gaseous state. It measures the tendency of an atom to accept an electron.
Electron Affinity: Electron affinity is the measure of the ability of an atom to accept an additional electron to form a stable negative ion. It represents the energy released when an electron is added to a neutral atom in the gaseous state, forming a negative ion.
Electron configuration: Electron configuration describes the distribution of electrons in an atom's orbitals. It follows principles such as the Aufbau principle, Pauli exclusion principle, and Hund's rule.
Electron Configuration: Electron configuration is the arrangement of electrons in an atom's electron shells and subshells, which determines the atom's chemical properties and behavior. This concept is fundamental to understanding the periodic table, periodic trends, and the reactivity of elements.
Electronegativity: Electronegativity is a measure of an atom's ability to attract and hold onto electrons within a chemical bond. It is a dimensionless quantity usually assigned values on the Pauling scale.
Electronegativity: Electronegativity is a measure of an atom's ability to attract shared electrons in a chemical bond. It is a fundamental property that influences the nature and strength of chemical bonds, as well as the physical and chemical properties of substances.
Fluorine: Fluorine is the lightest and most reactive of the halogen group of elements. It is a highly corrosive, pale yellow gas that is the most electronegative element on the periodic table. Fluorine's unique properties and reactivity make it an important element in various chemical and industrial applications.
Germanium: Germanium is a metalloid element with the atomic number 32, belonging to group 14 of the periodic table. It is a hard, grayish-white material that is used in various electronic and semiconductor applications due to its unique properties.
Gold: Gold is a precious, dense, and highly valued metal that has been prized throughout human history for its unique properties and applications. It is a transition metal that is widely used in various industries, from jewelry and electronics to medicine and dentistry.
Groups: Groups are vertical columns in the periodic table, also known as families. Elements within a group share similar chemical properties due to having the same number of valence electrons.
Groups: Groups are the vertical columns in the periodic table of elements, which organize elements with similar chemical properties and behaviors. They are a fundamental organizing principle that allows for the predictable classification of elements based on their electronic configuration and reactivity.
Hydroxides: Hydroxides are chemical compounds containing the hydroxide ion, $OH^{-}$. They often form when metals react with water or oxygen.
Hydroxides: Hydroxides are a class of compounds consisting of a metal or polyatomic cation bonded to one or more hydroxide (OH-) anions. They are ionic compounds that play a crucial role in acid-base chemistry and the classification of chemical reactions.
Inner transition metals: Inner transition metals are elements found in the f-block of the periodic table, comprising the lanthanides and actinides. They are characterized by having electrons fill their f-orbitals.
Insulators: Insulators are materials that have a very high resistance to the flow of electric current, effectively preventing the transmission of electricity. They are essential components in electrical and electronic systems, ensuring the safe and efficient operation of various devices.
Intermolecular forces: Intermolecular forces are the forces of attraction and repulsion between molecules that influence the physical properties of substances. These forces are weaker than intramolecular forces, which hold atoms together within a molecule.
Intermolecular Forces: Intermolecular forces are the attractive or repulsive forces that exist between molecules, as opposed to the intramolecular forces that hold atoms together within a molecule. These forces play a crucial role in determining the physical properties and behavior of substances across various topics in chemistry, including non-ideal gas behavior, the properties of liquids, phase transitions, and the dissolution process.
Iodine: Iodine is a essential trace mineral that plays a vital role in various physiological processes, particularly in the regulation of thyroid function. It is a member of the halogen group of elements and is known for its distinctive violet-blue color and unique chemical properties.
Ionization energy: Ionization energy is the amount of energy required to remove an electron from a gaseous atom or ion. It is a key property that influences an element's reactivity and chemical behavior.
Ionization Energy: Ionization energy is the amount of energy required to remove an electron from an atom or molecule, forming a positively charged ion. This property is fundamental in understanding the periodic trends and chemical reactivity of elements, as it reflects the strength of the attraction between the nucleus and the outermost electrons.
Iron: Iron is a chemical element that is essential for many vital processes in the human body. It is a transition metal that plays a crucial role in various topics in chemistry, including atomic structure, the periodic table, chemical nomenclature, corrosion, periodicity, and the occurrence, preparation, and properties of transition metals and their compounds.
Lanthanides: Lanthanides are a series of 15 metallic elements from lanthanum (La) to lutetium (Lu) in the periodic table. They are known for their high magnetic susceptibility and luminescent properties.
Lanthanides: The lanthanides are a group of 15 elements in the periodic table, also known as the f-block or inner transition metals. They are characterized by the filling of the 4f electron shell and exhibit similar chemical properties due to their shared electronic configuration.
Lead: Lead is a dense, malleable, and highly versatile metallic element that has been used extensively throughout history in various applications. In the context of periodicity, lead's unique properties and position on the periodic table make it an important topic of study.
Lithium: Lithium is a soft, silver-white alkali metal that is the lightest of all metals. It is highly reactive and must be stored in an inert atmosphere or oil to prevent it from reacting with air or water. Lithium's unique properties and position on the periodic table make it a key element in understanding periodic trends and the organization of elements.
Lithium ion batteries: Lithium-ion batteries are rechargeable electrochemical cells that use lithium ions as the primary component of their electrochemistry. They are widely used in portable electronics and electric vehicles due to their high energy density and efficiency.
Main Group Elements: Main group elements, also known as representative elements, are the elements found in the s and p blocks of the periodic table. These elements make up the majority of the periodic table and are characterized by their stable valence electron configurations and tendency to form ionic or covalent compounds.
Malleable: Malleable refers to the ability of a material to be hammered, pressed, or rolled into different shapes without breaking or cracking. It is a physical property that allows materials to be deformed plastically under compressive stress without losing their structural integrity.
Metallic Bonding: Metallic bonding is the type of chemical bond that holds metal atoms together in a metallic crystal structure. It is characterized by a sea of delocalized valence electrons that are shared among the positively charged metal ions, resulting in the unique properties associated with metals.
Metalloid: Metalloids are elements with properties intermediate between metals and nonmetals. They can exhibit characteristics of both categories depending on the conditions.
Metalloids: Metalloids are elements with properties intermediate between metals and nonmetals. They are found along the staircase line on the Periodic Table.
Metalloids: Metalloids are a group of elements that exhibit properties intermediate between metals and nonmetals. They have characteristics that are a blend of metallic and nonmetallic traits, making them unique in their behavior and placement on the periodic table.
Metals: Metals are elements that are typically characterized by their ability to conduct electricity and heat, malleability, ductility, and a shiny appearance. They tend to lose electrons and form positive ions in chemical reactions.
Metals: Metals are a group of elements on the periodic table that are characterized by their shiny appearance, high electrical and thermal conductivity, and ability to form positive ions. They are essential components in many materials and play a crucial role in various chemical and industrial processes.
Molecular Bonding: Molecular bonding refers to the formation of chemical bonds between atoms, which allows them to combine and create stable molecules. This process is fundamental to the study of chemistry, as it governs the structure and properties of various substances.
Nitrogen: Nitrogen is a chemical element with the atomic number 7 and the symbol N. It is a colorless, odorless, and tasteless gas that makes up approximately 78% of the Earth's atmosphere. Nitrogen is an essential element for life, playing crucial roles in various chemical and biological processes.
Nitrogen fixation: Nitrogen fixation is the process by which molecular nitrogen ($N_2$) in the atmosphere is converted into ammonia ($NH_3$) or related nitrogenous compounds in soil. This process is essential for making nitrogen available to living organisms.
Noble gases: Noble gases are a group of chemical elements with similar properties that are found in Group 18 of the periodic table. They are characterized by their lack of reactivity due to having a complete valence electron shell.
Noble Gases: The noble gases are a group of six highly stable, nonreactive chemical elements found in group 18 of the periodic table. They include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). These gases are characterized by their full valence electron configuration, making them extremely unreactive under normal conditions.
Nonmetals: Nonmetals are elements that typically have high ionization energies and electronegativities. They are poor conductors of heat and electricity and can be found on the right side of the periodic table.
Nonmetals: Nonmetals are a group of elements on the periodic table that do not possess the characteristic metallic properties of metals. They are generally poor conductors of heat and electricity, have high ionization energies, and form covalent bonds with other elements.
Octet rule: The octet rule states that atoms tend to form bonds in such a way that they achieve eight electrons in their valence shell, gaining a stable electron configuration similar to noble gases. This rule is fundamental for understanding molecular structures and chemical bonding.
Octet Rule: The octet rule is a fundamental concept in chemistry that states that atoms tend to form stable configurations by attaining a full outer electron shell, typically containing eight electrons. This principle helps explain the formation of ionic and covalent bonds, as well as the stability of various chemical compounds.
Osmium: Osmium is a rare, hard, and dense transition metal that is part of the platinum group. It is known for its unique properties and applications in various industries.
Oxyanions: Oxyanions are polyatomic ions that contain one or more oxygen atoms bonded to another element, typically a non-metal. They often carry a negative charge due to the presence of extra electrons.
Oxygen: Oxygen is a highly reactive nonmetallic element that is essential for most forms of life. It is the third most abundant element in the universe and the most abundant element on Earth's crust. Oxygen plays a crucial role in various chemical and biological processes, including respiration, combustion, and oxidation-reduction reactions.
P-orbital: A p-orbital is one of the four types of atomic orbitals in an atom, representing the second energy level or shell. P-orbitals are higher in energy than s-orbitals and are characterized by a more complex shape with three lobes arranged in a specific orientation.
Passivation: Passivation is the process by which a material becomes less affected by environmental factors such as air or water, often forming a protective oxide layer. This increases the material's resistance to corrosion and chemical reactions.
Periodic Table: The periodic table is a tabular arrangement of chemical elements organized by their atomic number, electron configuration, and recurring chemical properties. It serves as a fundamental tool in chemistry, providing a systematic way to classify and understand the behavior of elements based on their position within the table.
Periods: Periods are the horizontal rows in the periodic table. They indicate the number of electron shells an atom possesses.
Periods: Periods, in the context of chemistry, refer to the horizontal rows in the periodic table of elements. These rows group elements with similar physical and chemical properties, and the position of an element within a period provides important information about its atomic structure and behavior.
Phosphorus: Phosphorus is a multivalent nonmetal that is essential for life, playing a crucial role in various biological and chemical processes. It is a key component of the human body and is widely distributed in nature, making it an important element across the fields of chemistry, biology, and geology.
Potassium: Potassium is a soft, silvery-white metallic element that is the seventh most abundant element in the Earth's crust. It is an essential mineral for the proper functioning of the human body, playing a crucial role in maintaining fluid balance, nerve transmission, and muscle contraction.
Principal quantum number: The principal quantum number, denoted as $n$, indicates the main energy level or shell occupied by an electron in an atom. It is a positive integer that determines the size and energy of the orbital.
Principal Quantum Number: The principal quantum number is a fundamental concept in quantum mechanics that describes the energy levels of electrons within an atom. It is a positive integer that represents the shell or energy level in which an electron resides, and it plays a crucial role in understanding the structure and behavior of atoms across various topics in chemistry.
Reactivity: Reactivity refers to the tendency of a substance or element to undergo chemical reactions. It describes the ease with which a material can participate in chemical processes, forming new compounds or breaking down existing ones. Reactivity is a fundamental concept in chemistry that is closely tied to the physical and chemical properties of substances, as well as their periodic behavior.
Representative elements: Representative elements are the elements found in Groups 1, 2, and 13-18 of the periodic table. They display a wide range of physical and chemical properties and include metals, metalloids, and nonmetals.
Representative metals: Representative metals, also known as main-group metals, are elements found in groups 1 and 2 of the periodic table. They exhibit predictable chemical properties and are essential for understanding periodic trends.
Rhenium: Rhenium is a rare, silvery-white, dense, and hard transition metal that is found in the periodic table. It is known for its high melting point, corrosion resistance, and use in various industrial and technological applications.
Rubidium: Rubidium is a soft, silvery-white alkali metal that is the second most electropositive and reactive of the stable elements. It is commonly found in the Earth's crust and has various applications in electronics and nuclear technology.
S-Orbital: The s-orbital is one of the fundamental electron orbital types in an atom, characterized by a spherical shape and the lowest energy level. It plays a crucial role in understanding the periodic trends and properties of elements within the context of periodicity.
Semiconductors: Semiconductors are materials that have electrical conductivity properties that fall between those of conductors, such as metals, and insulators, such as glass. They are essential components in a wide range of electronic devices, including transistors, integrated circuits, and photovoltaic cells.
Shielding Effect: The shielding effect refers to the phenomenon where the presence of inner electron shells in an atom reduces the effective nuclear charge experienced by the outermost valence electrons. This shielding of the nucleus by the inner electron shells influences the chemical and physical properties of elements.
Silicon: Silicon is a chemical element that is classified as a metalloid, meaning it has properties that are intermediate between those of metals and nonmetals. It is the second most abundant element in the Earth's crust, after oxygen, and is a critical component in many technological applications and materials.
Silver: Silver is a lustrous, soft, and malleable transition metal with a wide range of applications in various industries, including electronics, jewelry, and photography. It is known for its unique properties, such as high electrical and thermal conductivity, as well as its antimicrobial and corrosion-resistant characteristics.
Sodium: Sodium is a soft, silvery-white, highly reactive alkali metal that is essential for various physiological processes in the human body. It is a key element in the context of atomic structure, the periodic table, chemical nomenclature, formula mass, periodic variations in element properties, and periodicity.
Sulfur: Sulfur is a naturally occurring chemical element that is essential for life and has a wide range of applications in various industries. It is a versatile element that plays a crucial role in the periodic variations of element properties, the periodicity of the elements, the structure and general properties of the nonmetals, and the occurrence, preparation, and properties of sulfur itself.
Transition Metals: Transition metals are a group of elements in the periodic table that are characterized by their partially filled d-orbitals and ability to form various oxidation states. They exhibit unique chemical and physical properties that make them essential for numerous applications in science, industry, and everyday life.
Tungsten: Tungsten is a dense, hard, and refractory transition metal that is found in the Earth's crust. It has a high melting point, excellent thermal and electrical conductivity, and is used in a variety of industrial and technological applications.
Valence electrons: Valence electrons are the outermost electrons of an atom and are involved in forming chemical bonds. They determine an element's chemical properties and reactivity.
Valence Electrons: Valence electrons are the outermost electrons in an atom that participate in chemical reactions and bonding. They are the electrons in the highest occupied energy level of an atom and are responsible for an element's chemical properties and behavior.