2.6 Ionic and Molecular Compounds
3 min read•june 24, 2024
Chemical compounds come in two main flavors: ionic and molecular. are like salt, with charged particles held together by strong electrical forces. , like water, have atoms sharing electrons in .
Knowing the periodic table helps predict compound types. Metals on the left tend to form with nonmetals on the right. Nonmetals usually form with each other. Understanding these patterns is key to predicting chemical behavior.
Ionic and Molecular Compounds
Ionic vs molecular compounds
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- Ionic compounds consist of positively charged (metals) and negatively charged (nonmetals) held together by strong electrostatic forces called ()
- Form when metals transfer electrons to nonmetals resulting in high melting and boiling points
- Conduct electricity when dissolved in water or molten due to the presence of mobile ions ( solution)
- Molecular compounds composed of atoms held together by formed by the sharing of electrons between nonmetals ()
- Held together by relatively weaker intermolecular forces such as or
- Generally have lower melting and boiling points compared to ionic compounds ( sublimes at -78.5 ℃)
- Usually do not conduct electricity in any state because they do not contain mobile ions ()
Compound types from periodic trends
- Ionic compounds typically form between metals on the left side of the periodic table and nonmetals on the right side ()
- Elements with large differences in are more likely to form ionic bonds ()
- Molecular compounds typically form between nonmetals on the right side of the periodic table ()
- Elements with similar or slightly different values tend to share electrons and form covalent bonds ()
- Electronegativity trends in the periodic table play a key role in predicting bond types
- Increases from left to right across a period as the decreases and increases (C < N < O < F)
- Decreases from top to bottom within a group as the atomic radius increases and effective nuclear charge decreases (F > Cl > Br > I)
Formulas of ionic compounds
- Determine the charges of the cation and anion
- Metal cations usually have positive charges equal to their group number ( from Group 1, from Group 2)
- Nonmetal anions usually have negative charges equal to (8 - group number) ( from Group 16, from Group 15)
- Balance the charges of the cation and anion to achieve a neutral compound
- The sum of the charges in the formula must equal zero
- Use subscripts to indicate the number of each ion needed for charge balance ( and → )
- Examples showcase the application of these rules
- Potassium bromide: K⁺ and Br⁻ →
- Calcium fluoride: Ca²⁺ and F⁻ →
- Aluminum sulfide: Al³⁺ and S²⁻ →
Electronic Structure and Bonding
- The guides the formation of stable compounds, where atoms tend to gain, lose, or share electrons to achieve a full outer shell of 8 electrons
- , the outermost electrons of an atom, play a crucial role in chemical bonding and reactivity
- provide a visual representation of and bonding in molecules
- in molecules arises from uneven distribution of electron density
- Dipole moments quantify the degree of charge separation in polar molecules
Key Terms to Review (47)
Al₂O₃: Al₂O₃, or aluminum oxide, is a chemical compound composed of two aluminum atoms and three oxygen atoms. It is a hard, white, and inert material that is widely used in various industrial and commercial applications due to its unique physical and chemical properties.
Al₂S₃: Al₂S₃, or aluminum sulfide, is an ionic compound composed of two aluminum atoms and three sulfur atoms. It is an important compound in the context of ionic and molecular compounds, as it demonstrates the principles of ionic bonding and the formation of polyatomic ions.
Al³⁺: Al³⁺ is the chemical symbol representing the aluminum ion, which has a charge of 3+ due to the loss of three valence electrons. This ion is an important component in the study of ionic and molecular compounds.
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.
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.
Bond dipole moment: A bond dipole moment is a measure of the polarity of a chemical bond within a molecule. It occurs due to the difference in electronegativity between two bonded atoms, causing a separation of electric charge.
Ca²⁺: Ca²⁺ is the calcium ion, a positively charged ion with a charge of +2. It is an important ion in the context of ionic and molecular compounds, as it can form ionic bonds with other elements to create various chemical compounds.
CaF₂: CaF₂, or calcium fluoride, is an ionic compound consisting of calcium (Ca) and fluorine (F) atoms. It is a naturally occurring mineral known as fluorite and is widely used in various industrial and commercial applications.
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.
CH₄: CH₄, also known as methane, is the simplest alkane hydrocarbon compound with the chemical formula CH₄. It is a tetrahedral molecule composed of one carbon atom covalently bonded to four hydrogen atoms. Methane is an important compound in the context of ionic and molecular compounds, as it is a prime example of a molecular compound formed through covalent bonding.
Cl₂: Cl₂ is the chemical formula for chlorine gas, a diatomic molecule consisting of two chlorine atoms covalently bonded together. This term is important in the context of ionic and molecular compounds as well as reaction stoichiometry, as chlorine is a highly reactive element that forms various compounds and participates in numerous chemical reactions.
CO₂: CO₂, or carbon dioxide, is a colorless, odorless gas that is produced as a byproduct of various chemical processes, including cellular respiration and the combustion of fossil fuels. It is a crucial compound in the context of ionic and molecular compounds, as it plays a vital role in numerous chemical reactions and environmental processes.
Covalent bonds: A covalent bond is a type of chemical bond where two atoms share one or more pairs of electrons to achieve a stable electron configuration. These bonds typically form between non-metal atoms with similar electronegativities.
Covalent Bonds: Covalent bonds are chemical bonds formed by the sharing of electrons between two atoms. These bonds are characterized by the stable arrangement of shared electron pairs, which helps to satisfy the valence electron requirements of the participating atoms.
Dipole Moment: Dipole moment is a measure of the separation of positive and negative electrical charges within a molecule or system. It is a vector quantity that describes the magnitude and direction of the charge separation, and it plays a crucial role in understanding the polarity and intermolecular interactions of molecules.
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.
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.
H₂O: H₂O, commonly known as water, is a chemical compound consisting of two hydrogen atoms and one oxygen atom. It is a vital substance that plays a crucial role in various chemical and biological processes, including those related to ionic and molecular compounds as well as reaction stoichiometry.
HCl: HCl, or hydrogen chloride, is a chemical compound consisting of one hydrogen atom and one chlorine atom. It is a colorless, corrosive gas that has a wide range of applications and plays a crucial role in various chemical processes and reactions.
Hydrogen Bonding: Hydrogen bonding is a type of dipole-dipole intermolecular force that occurs when a hydrogen atom covalently bonded to a highly electronegative element, such as nitrogen, oxygen, or fluorine, experiences an attractive force with another nearby highly electronegative element. This attractive force is significantly stronger than a typical dipole-dipole interaction and has a significant impact on the physical and chemical properties of various compounds.
Ionic bonds: Ionic bonds are a type of chemical bond formed through the electrostatic attraction between oppositely charged ions. Typically, these bonds form when a metal donates one or more electrons to a non-metal.
Ionic Bonds: Ionic bonds are a type of chemical bond that forms between a metal and a nonmetal through the transfer of electrons. This electrostatic attraction between oppositely charged ions is a fundamental concept in understanding the structure and properties of ionic compounds.
Ionic compound: An ionic compound is a chemical compound composed of ions held together by electrostatic forces termed ionic bonding. These compounds typically form between metals and nonmetals.
Ionic Compounds: Ionic compounds are chemical compounds formed by the electrostatic attraction between oppositely charged ions. They are created when a metal atom loses one or more electrons to a nonmetal atom, resulting in the formation of positively and negatively charged ions that are held together by strong ionic bonds.
K⁺: K⁺ is the chemical symbol for the potassium cation, a positively charged ion of the element potassium. Potassium is an essential mineral that plays a crucial role in various physiological processes, including maintaining proper fluid balance, nerve function, and muscle contraction.
KBr: KBr, or potassium bromide, is an ionic compound consisting of the potassium cation (K+) and the bromide anion (Br-). It is an important compound in the context of ionic and molecular compounds, as it demonstrates the formation of ionic bonds and the properties associated with ionic compounds.
KCl: KCl, or potassium chloride, is an ionic compound consisting of one potassium (K+) cation and one chloride (Cl-) anion. It is an important compound in the context of ionic and molecular compounds, molarity, and the occurrence and preparation of representative metals.
Lewis Structures: Lewis structures, also known as Lewis dot diagrams, are a visual representation of the bonding between atoms in a molecule. They depict the arrangement of atoms and the sharing or transfer of valence electrons, providing insights into the structure and properties of chemical compounds.
LiF: LiF, or lithium fluoride, is an ionic compound composed of lithium ions (Li\(^+\)) and fluoride ions (F\(^-\)). This compound is characterized by the transfer of an electron from lithium to fluorine, resulting in the formation of a strong ionic bond. Due to its ionic nature, LiF has distinct properties that connect to concepts such as electrical conductivity and solubility in water.
Molecular compounds: Molecular compounds consist of molecules formed by atoms of two or more different nonmetals sharing electrons through covalent bonds. They typically have low melting and boiling points compared to ionic compounds.
Molecular Compounds: Molecular compounds are chemical compounds formed by the covalent bonding of two or more atoms of different elements. They are distinct from ionic compounds, which are held together by electrostatic forces between oppositely charged ions. Molecular compounds are the focus of organic chemistry and are essential in understanding the structure and behavior of various substances.
Monatomic ions: Monatomic ions are single atoms that have gained or lost electrons, resulting in a net electrical charge. They can be either positively charged (cations) or negatively charged (anions).
NaBr: NaBr, or sodium bromide, is an ionic compound composed of the sodium (Na+) and bromide (Br-) ions. It is an important halogen compound that has various applications and properties related to ionic and molecular compounds, as well as the occurrence, preparation, and properties of halogens.
NaCl: NaCl, commonly known as sodium chloride, is a chemical compound that consists of one sodium atom (Na) and one chlorine atom (Cl) bonded together. It is an ionic compound that is essential for various biological and industrial processes, and it is the primary component of table salt.
O²⁻: O²⁻ is the chemical formula for the superoxide ion, a reactive oxygen species that plays important roles in both ionic and molecular compounds. It is formed when oxygen molecules gain an extra electron, resulting in a negatively charged ion.
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.
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.
P³⁻: P³⁻ is a polyatomic ion consisting of a single phosphorus atom bonded to three oxygen atoms, resulting in a net negative charge of 3. This ion is an important component in ionic and molecular compounds, particularly in the context of chemistry topics related to ionic and molecular structures.
Polarity: Polarity refers to the unequal distribution of electrons within a molecule, resulting in the creation of partially positive and partially negative regions. This concept is fundamental in understanding the properties and behavior of ionic, molecular, and organic compounds.
S²⁻: S²⁻ is the sulfide ion, a negatively charged ion consisting of two sulfur atoms. It is an important ionic species in the context of ionic and molecular compounds.
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.
Van der Waals forces: Van der Waals forces are weak intermolecular forces that arise from the interactions between induced or permanent dipoles in molecules. They play a crucial role in determining the physical properties of liquids and solids.
Van der Waals Forces: van der Waals forces are a type of weak intermolecular attractive forces that arise between neutral atoms or molecules. These forces are responsible for the non-ideal behavior of gases, the properties of liquids and solids, and the structure and general properties of nonmetals and noble gases.