Nonmetals and Covalent Compounds

Nonmetals and Their Molecular Compounds Structure and Properties

• Nonmetals combine to form binary covalent compounds.
• Electrons are shared between atoms in covalent bonds.
• Molecular formulas represent the number and types of atoms in a molecule.

IUPAC Nomenclature

• The International Union of Pure and Applied Chemistry (IUPAC) provides naming conventions for chemical compounds.
• Electronegativity is a key factor determining the order of elements when writing a compound's name.

Rules for Naming Covalent Compounds

• Elements closer to the left side of the periodic table are named first.
• Within a group, the lower element is named first.
• Group 13-15 elements are listed before hydrogen.
• Hydrogen is listed first when bonded with elements in Groups 16-17.

Polar Covalent Bonds

• Atoms with differing electronegativities share electrons unequally.

Nonpolar Covalent Bonds

• Electrons are shared equally between atoms due to similar or identical electronegativity.

Electronegativity

• It measures the strength with which an atom attracts shared electrons in a bond.

Steps for Drawing Lewis Dot Structures in Covalent Compounds

• Determine the total number of valence electrons.
• Identify the central atom (least electronegative) and arrange atoms around it.
• Place a bonding pair of electrons between adjacent atoms to form single bonds.

Single Bonds

• Two atoms share one pair of electrons.

Multiple Bonds

• Two or three pairs of electrons are shared between two atoms, forming double or triple bonds.

Drawing Lewis Dot Structures for Polyatomic Ions

• Add or subtract electrons to account for the ion's charge.
• Follow steps 1-4 for covalent compounds, and then enclose the structure in brackets, placing the charge outside the bracket.

Resonance Structures

• Two or more Lewis structures can depict a molecule with delocalized electrons.

Expanded Octet

• Some elements can have more than eight valence electrons in their outer shell, particularly those in the third period and beyond.

The Geometry of Simple Compounds

• Simple compounds consist of two or more elements bonded together.
• Molecular geometry describes the three-dimensional arrangement of atoms in a molecule.

VSEPR Theory

• The Valence Shell Electron Pair Repulsion Theory helps predict molecular geometry.

Linear Geometry

• The central atom is bonded to two other atoms at 180 degrees.

Trigonal Planar Geometry

• The central atom is surrounded by three other atoms, forming a 120-degree triangular plane.

Angular Geometry

• The central atom is bonded to two other atoms with a bond angle less than 180 degrees.

Tetrahedral Geometry

• The central atom is surrounded by four other atoms, forming a tetrahedron with 109.5-degree bond angles.

Trigonal Bipyramidal Geometry

• The central atom is surrounded by five other atoms.

Octahedral Geometry

• The central atom is surrounded by six other atoms.

Determine the Polarity of Simple Molecules

• Molecular polarity is determined by bond polarity and molecular geometry.

Factors Influencing Molecular Polarity

• Electronegativity difference between bonded atoms: Greater differences create more polar bonds.
• Molecular geometry: Symmetrical molecules tend to be nonpolar.

Covalent Compound

• Sharing of electrons between atoms.

Ionic Compound

• Formed by electrostatic attraction between positive and negative ions.

Bond Polarity

• The relative tendency of an atom to attract electrons toward itself in a bond.

Molecular Polarity

• The overall polarity of a molecule, considering both bond polarity and molecular geometry.

Functional Groups

• Specific groups of atoms within a molecule that influence its chemical reactivity and properties.

Organic Compounds

• Compounds containing carbon and hydrogen, or derivatives of them.

Hydrocarbons

• Composed of carbon and hydrogen, divided into alkanes, alkenes, alkynes, and aromatics.

Hydrocarbon Derivatives

• Hydrocarbons where at least one hydrogen atom is substituted with another atom or group.

Naming Hydrocarbons

• Prefixes indicate the number of carbon atoms in the longest continuous chain.
• Suffixes "-ane", "-ene", "-yne" denote single, double, or triple bonds.

Aromatic Hydrocarbons

• Contain a ring of carbon atoms with delocalized pi electrons, giving them unique properties.

Hydrocarbon Derivatives

• Halides: Halocarbons with halogen atoms (F, Cl, Br, I) attached.
• Alcohols: Contain a hydroxyl group (-OH) attached to a carbon atom.
• Ethers: Oxygen atom links two hydrocarbon groups.

Aldehydes & Ketones

• Key functional group: Carbonyl group (C=O).
• Aldehydes: Carbonyl group at the end of the carbon chain.
• Ketones: Carbonyl group located within the carbon chain.

Carboxylic Acids

• Contain a carboxyl group (-COOH).
• Acidic and able to donate hydrogen ions.

Esters

• Derived from carboxylic acids by replacing the -OH group with an alkyl group.

Amines

• Contain nitrogen atoms with hydrogen or hydrocarbon groups attached.
• Basic (alkaline) and often have a fishy smell.

Amides

• Related to carboxylic acids with the -OH group replaced by an amine (-NH2).
• More stable than esters.

Nitriles

• Contain a cyano group (C=N), carbon triple-bonded to nitrogen.

Structural Isomerism

• Molecules with the same molecular formula but different arrangements of atoms.

Types of Structural Isomerism

• Chain Isomerism: Different arrangements of carbon atoms in straight or branched chains.
• Positional Isomerism: Same carbon chain but different functional group positions.
• Functional Group Isomerism: Same atoms but different functional groups.

Stereoisomerism

• Molecules with the same molecular formula and connectivity but different spatial arrangements.

Types of Stereoisomerism

• Cis-trans Isomers (Geometric Isomers): Different arrangements of substituents around a double bond.
• Enantiomers (Optical Isomers): Mirror images of each other that are not superimposable.
• Diastereomers: Stereoisomers that are not mirror images of each other.

Simple Reactions of Organic Compounds

• Combustion: Burning of organic compounds in oxygen to produce carbon dioxide and water.
• Addition Reaction: Addition of a molecule to a double or triple bond.
• Condensation Reaction: Two molecules combine to form a larger molecule with the elimination of a small molecule (e.g., water).
• Saponification: The reaction of a fat with a strong base (e.g., NaOH, KOH) to produce soap and glycerol.

Polymers

• Large molecules formed by joining repeating small units called monomers.
• Properties depend on the type and arrangement of monomers.

Tacticity

• Refers to the arrangement of pendant groups (side chains) along the polymer backbone.

Types of Polymers

• Isotactic polymers: Pendant groups are oriented on the same side of the backbone.
• Syndiotactic polymers: Pendant groups alternate sides of the backbone.
• Atactic polymers: Pendant groups have random orientations.

Polymerization

• The process of forming polymers.
• Step-growth polymerization: Polymerization proceeds stepwise, independent of chain growth.
• Chain-growth polymerization: Polymerization involves a chain reaction where monomers are added one at a time to a growing polymer chain.

Classification Based on Origins

• Natural polymers: Found in living organisms, formed through biological processes.
• Synthetic polymers: Man-made, made from commercially available compounds.

Classification Based on Monomer Types

• Homopolymer: Made up of one type of monomer.
• Heteropolymer: Made up of two or more different types of monomers.
• Copolymer: Made up of two or more different types of monomers in a specific arrangement.