Chapter 4 Flashcards
What is an ionic bond?
Strong electrostatic force of attraction
between cations and anions in an ionic compound.
What is an ion?
Electrically charged atom or molecule (contains unequal numbers of protons and electrons).
____ crystals are composed of alternating ____ and ____ ions (Two fairly toxic substances on their own combine to become something we absolutely cannot live without!) which are electrostatically attracted to one another by virtue of opposite charges
NaCl crystals are composed of alternating Cl- and Na+ ions ((Two fairly toxic substances on their own combine to become something we absolutely cannot live without!) which are electrostatically attracted to one another by virtue of opposite charges
During the formation of some compounds, atoms gain or lose electrons and form electrically charged particles called ____
Ions
You can use the ____ ____ to predict which ion species will form
Periodic table
What is bond length?
The bond length is the internuclear distance at which the lowest potential energy is achieved.
Covalent bond?
When electrons are “shared” and molecules form.
The distribution of ____ ____ in the HCl molecule is uneven. The electron density is greater around the ____ ____. The small, black dots indicate the location of the hydrogen and chlorine nuclei in the molecule. (b) Symbols ____ and ____ indicate the polarity of the H–Cl bond.
The distribution of electron density in the HCl molecule is uneven. The electron density is greater around the chlorine nucleus. The small, black dots indicate the location of the hydrogen and chlorine nuclei in the molecule. (b) Symbols δ+ and δ– indicate the polarity of the H–Cl bond.
What are the three bond types and what electronegativity difference is associated with them?
Pure (non-polar) covalent <0.4
Polar covalent 0.4 to 1.8
Ionic >1.8
What is nomenclature?
A collection of rules for naming things
How are compounds identified in nomenclature?
Compounds are identified by both their formula and name
What type of inorganic compounds will we learn to name?
Ionic and molecular binary compounds: composed of two elements.
Ionic compounds containing polyatomic ions.
Acids
What is a binary compound?
One that contains two elements
What is the basis for classifying chemical bounding?
The nature of attractive forces that hold atoms or ions together within a compound is the basis for classifying chemical bonding
Ionic bonds?
Electrons are transferred between atoms resulting in the formation of ions and electrostatic attraction to form salts
Covalent bonds?
electrons are shared between atoms to form molecules
Ionic compounds form ____?
Covalent compounds form ____?
Formula units
Molecules
Most of the transition metals and some main group metals can form ______________________________________ charges.
The charge of the metal ion is specified by a ____ ____ in parentheses after the _______________.
Most of the transition metals and some main group metals can form two or more cations with different charges.
The charge of the metal ion is specified by a Roman numeral in parentheses after the name of the metal.
What is a hydrate?
Compound, often ionic, that contains one or more water molecules bound within its crystals.
Hydrates may typically be dehydrated by heating to remove the bound water molecules, yielding the ____ compound.
Anhydrous
Two steps to naming hydrates?
- Name the anhydrous compound (per usual rules)
- Add the word hydrate with a Greek prefix denoting the number of water molecules
How are formulas for hydrates written?
Formulas for hydrates are written by appending the formula for water to the formula for the anhydrous compound, including a stoichiometric coefficient denoting the number of water molecules, and separated by a vertically centered dot
Examples:
copper(II) sulfate pentahydrate CuSO4·5H2O
calcium chloride monohydrate CaCl2·H2O
How are ionic compounds named?
Cation put first (Element name followed by roman numeral in parenthesis ONLY if more than one possible charge)
Anion second (ide ending if a binary compound and ion name if polyatomic)
How are covalent compounds named
More metallic element (one further to the left or further down) is named first
Then the name of the nonmetallic element with the suffix ending in ide
For BOTH elements the number of each is denoted by Greek prefixes.
In covalent naming:
When only one atom of the first element is present, the prefix ____ is usually not used.
When two vowels are adjacent, the ____ in the Greek prefix is usually dropped.
mono-
a (alpha)
Some compounds containing hydrogen are members of an important class of substances known as ____.
Many acids release hydrogen ions, ____, when dissolved in water
A mixture of an acid with water is given a ____ ____ to denote this property
Acids
H+
Special name
Thee steps to naming acids?
- The word “hydrogen” is changed to the prefix hydro–.
- The other nonmetallic element name is modified by adding the suffix –ic.
- The word “acid” is added as a second word.
What are oxyacids and in what way are they bonded?
Compounds that contain hydrogen, oxygen, and at least one other element, and are bonded in such a way as to impart acidic properties to the compound.
Typical oxyacids consist of hydrogen combined with a __________________.
Polyatomic, oxygen-containing ion
Four steps to naming oxyacids?
- Omit the hydrogen
- Start with the root name of the anion
- Replace -ate with -ic, or -ite with -ous
- Add “acid”
5 steps for determining Lewis structure?
- Determine the total number of valence (outer shell) electrons. For cations, subtract one electron for each positive charge. For anions, add one electron for each negative charge.
- Draw a skeleton structure of the molecule or ion, arranging the atoms around a central atom. (Generally, the least electronegative element should be placed in the center.) Connect each atom to the central atom with a single bond (one electron pair).
- Distribute the remaining electrons as lone pairs on the terminal atoms (except hydrogen), completing an octet around each atom.
- Place all remaining electrons on the central atom.
- Rearrange the electrons of the outer atoms to make multiple bonds with the central atom in order to obtain octets wherever possible.
What is a single bond?
A single shared pair of electrons
Octet rule?
The tendency of main group atoms to form enough bonds to obtain eight valence
electrons
Double bond?
Forms when two pairs of electrons are shared between a pair of atoms
Triple bond?
Forms when three electron pairs are shared by a pair of atoms
What are exceptions to the octet rule?
Odd-electron molecules
Electron-deficient molecules
Hypervalent molecules
What are odd electron molecues?
Molecules that contain an odd number of electrons free radicals
What are electron deficient molecules?
Molecules that contain a central atom that do have not have a full valence shell
Hypervalent molecules?
A central atom that is bonded to more molecules than expected based on the octet rule
What is formal charge?
Formal charge: hypothetical charge the atom would have if we could redistribute the electrons in the bonds evenly between the atoms
= # of valance shell electrons (free atom) - # lone pair electrons - 1/2 # bonding electrons
A molecular structure in which all formal charges are ____ is preferable to one in which some formal charges are not ____.
If the Lewis structure must have nonzero formal charges, the arrangement with the ____ ____ formal charges is preferable.
Lewis structures are preferable when adjacent formal charges are _________________________.
When we must choose among several Lewis structures with similar distributions of formal charges, the structure with the _________________________ is preferable.
A molecular structure in which all formal charges are zero is preferable to one in which some formal charges are not zero.
If the Lewis structure must have nonzero formal charges, the arrangement with the smallest nonzero formal charges is preferable.
Lewis structures are preferable when adjacent formal charges are zero or of the opposite sign.
When we must choose among several Lewis structures with similar distributions of formal charges, the structure with the negative formal charges on the more electronegative atoms is preferable.
What is resonance?
Resonance: if two or more Lewis structures with the same arrangement of atoms can be written for a molecule or ion, the actual distribution of electrons is anaverageof that shown by the various Lewis structures.
Describe resonance according to a nitrite molecule (NO2-)
Can be drawn in two different ways, depending on the location of the double bond
Experimental evidence shows that the bond lengths are identical for both N-O/N=O bonds, so the resonance forms (resonance hybrid) is the only structure that makes sense
What is bond angle?
The angle between any two bonds that include a common atom, usually measured in degrees
What is bond distance?
The distance between the nuclei of two bonded atoms along the straight line joining the nuclei
What is VSEPR Theory?
VSEPR Theory: valence shell electron-pair repulsion theory
VSEPR model assumes that electron pairs in the valence shell of a central atom will adopt an arrangement that minimizes repulsions between these electron pairs by maximizing the distance between them.
What do solid and dashed wedges indicate when drawing molecular structure?
Solid wedges = coming out of the page
Dashed lines = going into the page
Linear?
Trigonal planar?
Tetrahedral?
Trigonal bipyramidal?
Octahedral?
6 electron dense areas and bonds foms at 90 degrees
Resonance hybrid?
Experimental evidence shows that the bond lengths are identical for both N-O/N=O bonds, so the resonance forms (resonance hybrid) is the only structure that makes sense
What is the order of greatest repulsion to least repulsion between different kinds of e-pairs?
lone pair-lone pair > lone pair-bonding pair > bonding pair-bonding pair
What is the order of space occupied in different kinds of bonds and electron configurations?
lone pair > triple bond > double bond > single bond
Trigonal bipyramidal?
Axial position?
Equatorial position?
In trigonal bipyramidal geometry, lone pairs always occupy the ____ positions because of the availability of space
Equatorial
Bond dipole moment?
Dipole moments are a ____ quantity
Describe the equation?
Separation of partial positive and negative charges gives rise to a bond dipole moment
Dipole moments are a vector quantity (possess both magnitude and direction)
mu = Qr
mu = magnitude
Q = electronegative difference
r = distance between charges
If a molecule has separation of charge, it is called a ____ ____ or ____
If it lacks separation of charge, then the molecule is ____
Polar molecule or dipole
nonpolar
How is dipole moment determined?
We determine dipole moment by adding the bond moments in 3-D space, taking into account molecular structure
Molecules of high symmetry – egs., BF3, CH4, PF5 and SF6 – all the bonds are of identical polarity and the dipole moment is zero (they cancel), which yields ____-____ molecules
Molecules of less geometric symmetry, but which have equal bond moments, produce a non-zero dipole moment and ____ molecule
Molecules of high symmetry – egs., BF3, CH4, PF5 and SF6 – all the bonds are of identical polarity and the dipole moment is zero (they cancel), which yields non-polar molecules
Molecules of less geometric symmetry, but which have equal bond moments, produce a non-zero dipole moment and polar molecule
Molecules of high symmetry – egs., BF3, CH4, PF5 and SF6 – all the bonds are of identical polarity and the _________________ (____ ____), which yields non-polar molecules
Molecules of less geometric symmetry, but which have equal bond moments, produce a_______________ and polar molecule
Molecules of high symmetry – egs., BF3, CH4, PF5 and SF6 – all the bonds are of identical polarity and the dipole moment is zero (they cancel), which yields non-polar molecules
Molecules of less geometric symmetry, but which have equal bond moments, produce a non-zero dipole moment and polar molecule
