Chapter 6 - Ionic and Molecular Compounds

6.1 - Ions: Transfer of Electrons

• The stable electron arrangements in the outermost energy level are associated with the stability of the noble gases.

• Noble gasses have eight valence electrons, which is an octet, except for helium, with two electrons.

• In Groups 1A to 7A (1,2, 13 to 17), the atoms of elements achieve stability through loss, gain, or sharing in the formation of composites their valence electrons.

• Representative metals lose valence electrons to make positive ions (cations): Group 1A, Group 1+, Group 2A(2), Group 2+ and Group 3A(13), Group 3+.

• In response to metals, nonmetals gain electrons to form bytes that form negative ions (anions): group 5A (15), group 3-, group 6A (16), group 2- and group 7A (17), group 1-.

  

6.2 - Ionic Compounds

• In the formula of an ionic compound, the total positive and negative ionic load is balanced.
• A formula charging balance is achieved using subscripts after every symbol so that the total charge is zero.

6.3 - Naming and Writing Ionic Formulas

• The positive ion is first indicated by its name, followed by the negative ion name.
• Two element names of ionic compounds end with ide.
• The transition elements form cations with two or more ionic charges, apart from Ag, Cd, and Zn.
  • The cation's charge is determined by the total negative charge in the formulation, which is immediately named after the metal with a variable charge as a roman number.

6.4 - Polyatomic Ions

• A Polyatomic ion is a group of electrically load-bound, covalent atoms, such as the formulation CO3 2- for the carbonate ion.
• The names that end with ate or are mostly polyatomic ions.
  • A nonmetal and one or more atoms contain polyatomic ions.
• The NH4+ ammonium ion is a polyatomic positive ion
• If several polyatomic ions are used to balance the charge, parentheses include the polyatomic ion formula.

6.5 - Molecular Compounds: Sharing Electrons

• Non-metals share valence electrons in covalent bonds, which ensures that every atom has a stable electron set-up.
  • In a molecular compound, the first nonmetal uses its name; the second nonmetal uses the first syllable of its name, followed by the ideal element.
• The name of a two-atoms-molecular compound uses prefixes to indicate the subscriptions in the formulation.

6.6 - Lewis Structures for Molecules

• For all the atoms in the molecule, the total number of valence electrons is determined.
• In Lewis's structure, the central atom and each of the attached atoms is connected by a pair of electrons.
• All remaining valence electrons are used to complement the octets of the surrounding atoms and the central atom as solitary pairs.
• If octets are not completed, one or more lone electron pairs are placed as double or threefold connecting pairs

6.7 - Electronegativity and Bond Polarity

• Electronegativity is an atom's ability to attract electrons that it shares.

  • The electronegativity of metals is generally low, while nonmetals have high electronegativity.

• Atoms share electrons equally in a nonpolar covalent bond.

• The electrons are unequally divided into a polar covalent connection because they are attracted to the more electronegative atom.

• The atom is partly positive in a polar relationship (d+) and partly negative in the polar link with lower electronegativity (d+) (d-).

• Atoms forming ionic bonds differ greatly in electronegativity.

  

6.8 - Shapes of Molecules

• The shape of a molecule is based on the Lewis structure, the geometry of the electron group and the number of atoms connected.
  • The geometry of the electron group surrounding a central atom with 2 electron groupings is linear; the geometry is planar trigonal in three electron groupings, and geometry is tetrahedral in four electron groups.
• The shape is identical to the electron arrangement when all of the electron groups are attached to atoms.
• A central atom has a bending form of 120° with three groups of electrons and two bonded atoms.
  • There is a trigonal pyramid shape in a central atom with four different electron groups and three connected atoms.
• A central atom has a curved form at 109°, consisting of four electron groups and two bonded atoms.

6.9 - Polarity of Molecules and Intermolecular Forces

• Non-polar molecules have non-polar covalent links or a bonded atomic arrangement to waive dipole
• The dipoles do not cancel in polar molecules
  • Opposite loaded ions are held in ionic solids by ionic connections in a rigid structure.
• Intermolecular forces are known as dipole-dipole and hydrogen binding maintained together with the solid and liquid states of polar molecular compounds.
  • The weak attractions between temporary dipole known as dispersion forces form nonpolar compounds.