Ionic and Covalent Compounds

study notes, labs (phet), worksheets

ionic compounds

cation gives away electrons to anion, forming a bond; metal bonds to nonmetal

properties of ionic compounds

solids, high melting point, hard and rigid, soluble in water, conductive of electricity (when in a liquid state or in a solution)

transition metals charges?

form cations but tend to vary in charges

polyatomic ions

group of atoms covalently bonded together with a charge

writing ionic compounds

cation first, then anion; correct formula will be neutral (no charge); last few letters changed to -ide

write Ca²⁺ bonded to Br^-

CaBr₂ (calcium bromide)

magnesium oxide

MgO

writing transition metals

must include a roman numeral indicating the charge of that metal

FeO

Iron (II) Oxide

writing polyatomic ions

don’t change the ending of the polyatomic ions; if a subscript is needed, it follows the entire polyatomic ion (enclosed in parentheses)

Calcium Acetate

Ca(C₂H₃O₂)₂

lattice energy

energy required to separate ions within an ionic compound; shows bond strength of ionic compound

coulomb’s law

calculates force of attraction based on the charges of the ions and the distance between their nuclei

what happens to the lattice energy as ions get smaller

increases

what happens to the lattice energy as ions get more electronegative

increases

covalent bonds

happen when 2 or more atoms share electrons to complete their octet; between 2 nonmetals

properties of covalent compounds

weaker forces — low melting and boiling points; mostly liquids; poor conductors of electricity; can form a weak crystal lattice

bond dissasociation

the amount of energy required to break one covalent bond

bond disassociation energy for a triple covalent bond compared to single covalent bond

triple bonds have a higher bond disassociation energy

lewis dot structures for covalent bonds

bond represented by a line, two dots on one side represents a lone pair, space out each region around the central atom

resonance structures

when more than 1 valid lewis structure can be drawn for a molecule/ion

exceptions to octet rule

when atoms form a suboctet or expanded octet

suboctet

less than 8 electrons around the atom

example of suboctet

boron can only form bonds with 3 other atoms; 6 electrons around boron

expanded octet

more than 8 electrons around the atom

example of expanded octet

sulfur can form bonds with 6 atoms; 12 electrons in total

types of expanded octets

linear, trigonal bipyramidal, octahedral

VSEPR theory

electrons will repel each other and will spread out in their arrangement around the central atom as much as they can

linear

no lone pairs on central atom, arranged in a line

diatomic molecule

two of the same element bonded together

trigonal planar

3 bonds, no center lone pairs

tetrahedral

4 bonds, no central lone pairs

trigonal pyramidal

3 bonds, one lone pair (forms with N and P)

trigonal bipyramidal

5 bonds, no lone pairs

bent

2 bonds, 1-2 lone pairs (typically 2)

octahedral

6 bonds, no lone pairs

naming covalent compounds

-ide ending, each element has a prefix referring to the # of atoms (drop mono for the first element)

N₂O₄

dinitrogen tetroxide

prefixes for covalent compounds

mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca

electron geometry

arrangement of all electron groups (lone pairs & bonds) around the central atom

molecular geometry

only considers arrangement of atoms

electron geometry vs molecular geometry for NH₃

tetrahedral electron geometry; trigonal pyramidal molecular geometry

nonpolar covalent bonds

atoms with the same/similar electronegativity bonded together (ex: N-N, C-H)

polar covalent bonds

atoms pull on electrons unequally

dipole moment

in a polar covalent bond, electrons spend more time around one atom than the other, resulting in partial charges at different ends of the bond

molecular polarity

how equally distributed charges are around the atom

nonpolar molecule

either all nonpolar bonds or the same domains around the center atom

molecular polarity of BH₃

nonpolar; just Hs equally distributed around the B

polar molecule

different domains around the central atom

molecular polarity of PBr₃

polar molecule; lone pair amongst Brs

sigma bond

covalent bond where the orbitals directly overlap

pi bond

covalent bond where the orbitals overlap sideways

how many sigma and pi bonds are in a single bond?

1 sigma, 0 pi

how many sigma and pi bonds are in a double bond?

1 sigma, 1 pi

how many sigma and pi bonds are in a triple bond?

1 sigma, 2 pi

hybridization

when atomic orbitals mix to form a new atomic orbital

types of hybrid orbitals

sp, sp² , sp³