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Chemical Bonding

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rules for naming monatomic ions
1. when metals lose electrons, they become ions. Their name DOES NOT change
2. when nonmetals gain electrons, they become ions. Their name DOES change to the root of the element + -ide)
nonmetals ______ electrons
gain electrons
this gives them a negative charge and makes them anions
metals ____ electrons
lose electrons
this gives them a positive charge and they become cations
polyatomic ions
a tightly bound group of atoms that behaves as a unit and has a positive or negative charge
-usually end in -ite or -ate
rules for naming binary ionic compounds
step 1: write the name of the metal ion
step 2: write the name of the nonmetal ion
transition metals
the names of transition metals include their charge (in parenthesis) because charges are less predictable
rules for determining the chemical formula for binary ionic compounds
step 1: write the symbol of the metal ion
step 2: write the symbol of the nonmetal ion
step 3: determine the charges and balance
rules for determining the chemical formula for binary ionic compounds (transition metals)
step 1: write the symbol of the cation
step 2: write the symbol on the anion
step 3: determine charges and balance
rules for determining the chemical formula for ionic compounds (w/polyatomic ions)
step 1: write the symbol of the metal ion
step 2: write the symbol of the polyatomic ion
step 3: determine charges and balance
Covalent Bonding: Naming and Writing Chemical Formulas for Molecular Compounds
1. write the name of the first nonmetal

2. write the name of the second nonmetal, change it's ending to -ide

3. add prefixs to specify how many of each element are present
Naming Binary Acids
1. For aqueous acid solutions, start with 'hydro-'.
2. change the anion name to end with '-ic'
3. add the word 'acid' at the end

hydrochloric acid
Naming Ternary Acids (oxyacids)
1. If the polyatomic anion ends in "ate" take the root and add "ic"
2. If the polyatomic anion ends with "ite," then take the root and add "ous"
3. Add acid

- Do NOT use hydro as a prefix

chloric acid
sulfurous acid
Halogen Oxyacid Acid Families
Do not use the prefix "hydro"

Named the same as the other ones, just with different anions
ionic compounds
compounds that are composed of cations and anions
ionic bonds
the electrostatic attraction that binds oppositely charged ions together
- result of the TRANSFER of electrons
- responsible for holding ionic compounds together
formation of ionic compounds
- the transfer of electrons
- the electron will leave the part of the compound that has a low ionization energy and will go to the part of the compound that has a higher electron affinity/electronegativity
- the result of electrostatic attractions
chemical formula
shows the kinds and numbers of atoms in the smallest representative unit of a substance
formula unit
the lowest whole number ratio of the ions in an ionic compound
properties of ionic compounds
- crystalline solids at room temperature (hard, brittle)
- high melting point
- soluble in water
- poor conductor as a solid (able to conduct an electric current when melted or dissolved)
coordination number
the number of ions of opposite charge that surround an ion in a crystal
the result of the arrangement of ions in crystalline solids
coulomb's law
Fe- electrostatic force
q1 and q2- ionic charges
- q1= cation (bigger radii) and q2=anion (smaller radii)
r^2- distance b/w the charges (ionic radii)
k- constant value
molecular compounds
compounds that are composed of molecules
molecule
a neutral group of atoms that joined together by covalent bonds
covalent bonds
a bond formed by sharing electrons b/w atoms
properties of molecular compounds
- contain 2(+) nonmetals
- often gases or liquids at room temperature (some are solid)
- low melting/boiling point
- often insoluble in water (generally depends on solubility of the solvent)
-doesn't conduct electricity
octet rule
chemical compounds tend to for so that each atom, by gaining, losing, or sharing electrons, has an octet of electrons in the highest energy level (valence shell)
- the outer s and p orbitals are completely filled with a total of 8 electrons
exceptions to the octet rule
include those atoms that cannot fit 8 electrons and for those that can fit more than 8 electrons into their outermost energy orbital
- hydrogen: forms bonds in which it is only surrounded by 2 electrons
- helium: is stable with 2 valence electrons
- boron: has 3 valence electrons, so it tends to form bonds in which it is surrounded by 6 electrons
- main group elements in period 3 and up can form bonds with expanded valence, involving more than 8 electrons. D orbitals must be available for this to occur
formation of covalent bonds
- both nuclei repel each other as do electron clouds
- the nucleus of each atom attracts both electron clouds
- a covalent bond is formed
- attractive forces > repulsion forces
molecular formula
chemical formula of a molecular formula
- shows how many atoms of each element a molecule contains
- can describe molecules consisting or one element (all diatomic)
single covalent bond
one electron is shared
double covalent bond
2 electrons are shared
triple covalent bond
3 electrons are shared
multiple covalent bonds v. single
multiple are stronger but shorter- harder to break
polar covalent bonds
pair of electrons shared unequally by 2 atoms
properties of water
- adhesive/cohesive
- universal solvent
- less dense than a solid
- moderate temp (takes a lot to heat up)
nonpolar covalent bonds
pair of electrons shared equally by 2 atoms
- hydrocarbons: made up of only carbon and hydrogen
coordinate covalent bond
covalent bond in which one atom contributes both bonding electrons
- the shared electron pair comes from one of the bonding atoms
- in a structural formula, show the coordinate covalent bonds as arrows that point from the atom donating to the atom receiving
bond dissociation energy
the energy required to break the bond b/w two covalently bonded atoms
- a large bond dissociation energy corresponds to a strong covalent bond (triple/double)
resonance structure
a structure that occurs when its possible to draw 2(+) valid e- dot structures that have the same # of e- pairs for a molecule ion
sigma bond
(σ) a bond formed when two atomic orbitals combine for form a molecular orbital that is symmetrical around the axis connecting the two atomic nuclei
pi bond
(π) a covalent bond in which the bonding electrons are most likely to be found in sausage-shaped regions above and below the bond axis of the bonded atoms
sigma and pi bond review
- sigma and pi bonds are related to covalent bonding
- sigma and pi bonds are used to link quantum mechanics to bonding
- sigma and pi bonds help determine where the electrons are that are participating in the bonding
- all single bonds are sigma bonds (no pi bonds)
- all double bonds have 1 sigma and 1 pi bond
- all triple bonds have 2 sigma and 1 pi bond
VSEPR (stands for)
valence shell electron pair repulsion
VSEPR theory
states that repulsion between the sets of valence-level electrons surrounding an atom causes these sets to be oriented as far apart as possible
- electrons with neg charges repel each other which produce predictable shapes
VSEPR observations
- the actual, observed shape of a molecule is determined by the positions of the atoms only
- lone pairs can occupy space around the central atom. Unshared pairs still affect the geometry of the molecule because they still have negative charges that will repel other electrons
- double and triple bonds are rated in the same way as single bonds
- polyatomic ions are treated similarly to other mole rules
- CONSIDER ALL OF THE ELECTRON PAIRS PRESENT IN AND ION OR MOLECULE
linear
-2 atoms bonded to a central atom OR 2 atoms total
-no lone pairs of electrons around the central atom
- bond angle is 180
trigonal planar
-3 atoms bonded to a central atom
-no lone pairs of electrons around the central atom
-bond angle is 120
bent
-2 atoms bonded to a central atom
-1 OR 2 lone pairs of electrons around the central atom
- bond angle is 118 (1 lone pair) and 104.5 (2 lone pairs)
tetrahedral
-4 atoms bonded to a central atom
-no lone pairs of electrons
-bond angle is 109.5
trigonal pyramidal
-3 atoms bonded to a central atom
-1 lone pair of electrons around the central atom
-bond angle is 107
trigonal bipyramidal
-5 atoms bonded to a central atom
-no lone pairs of electrons around the central atom
-bond angles are 90 and 120
octahedral
-6 atoms bonded to a central atom
-no lone pairs of electrons around the central atom
-bond angles are 90 and 180
polar covalent bonds
a covalent bond between atoms in which the electrons are shared unequally
polar v. nonpolar covalent bonds
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polar vs. nonpolar molecules
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intermolecular forces and their impact
weaker than ionic and covalent bonds
help determine if a molecule is a solid, liquid, or gas
ionic forces
...
van der waals forces
dipole interactions and dispersion forces
two weakest attractions
dipole interactions
intermolecular forces resulting from the attraction of oppositely charged regions of polar molecules
dispersion forces
attractions between molecules caused by the electron motion on one molecule affecting the electron motion on the other through electrical forces; these are the weakest intreating between molecules
hydrogen bonds
attractive forces in which a hydrogen covalently bonded to a ver electronegative atom is also weakly bonded to an unshared electron pair of another electronegative atom
network solids
or network crystal, solids in which all of the atoms are covalently bonded to each other
properties of water
...
ionic compounds
compounds that are composed of cations and anions