General Chemistry- Bonding and Chemical Interactions Flashcards
Most atoms can form what?
Molecules
What atoms are the exception to forming molecules?
The noble gases
How are the atoms in molecules held together?
Chemical bonds
What are chemical bonds?
Strong attractive forces
How are chemical bonds formed?
The interaction of the valence electrons of the combining atoms.
Compounds usually have similar or different chemical and physical properties as the elements that make them up?
Very different
For many molecules, the atoms combine based on what rule?
Octet rule
What is the octet rule?
An atom tends to bond with other atoms so that it has eight electrons in its outermost shell, thereby forming a stable electron configuration similar to that of the noble gases
Why is the octet rule on a rule of thumb?
There are more elements that can be exceptions to the rule than those that follow the rule.
Which elements are exceptions to the octet rule?
Hydrogen Lithium Beryllium Boron All elements in period 3 and greater
Which elements are stable with fewer than 8 electrons?
Hydrogen (2) Helium (2) Lithium (2) Beryllium (4) Boron (6)
Which elements are stable with an expanded octet?
Elements in period 3 or greater
Phosphorus (10)
Sulfar (12)
Chlorine (14)
What elements are another example of an exception to the octet rule?
An molecule with an odd number of valence electrons cannot distribute those electrons to give eight to each atom.
What is an example of an odd number molecule?
Nitric Oxide (NO)- (11)
What are the common elements that almost always abide by the octet rule?
Carbon Nitrogen Oxygen Fluorine Sodium Magnesium
What are the two types of chemical bonds?
Ionic
Covalent
What occurs during ionic bonding?
One or more electrons from an atom with a low ionization energy, typically a metal, are transferred to an atom with a high electron affinity, typically a nonmetal.
What holds the ionic bonds togethere?
Electrostatic attraction between opposite charges
The electrostatic attraction in ionic bonds creates what?
Lattice structures consisting of repeating rows of cations and anions, rather than individual molecular bonds
What occurs in covalent bonding?
An electron pair is shared between two atoms, typically nonmetals, that have relatively similar values of electronegativity.
What determines the polarity in a covalent bond?
The degree to which the pair of electrons is shared equally or unequally between the two atoms
If the electron pair is shared equally in a covalent bond, it is _________?
Nonpolar
If the electron pair is shared unequally, the bond is ________________?
Polar
When is a bond called coordinate covalent?
If both of the shared electrons are contributed by only one of the two atoms
What is an example of nonpolar covalent bonding?
Diatomic fluorine
What do covalent compounds consist of?
Individually bonded molecules
Ionic bonds form between atoms that have ___________ ________.
Significantly different electronegativities
The atoms become what in ionic bonding?
cations and anions
The ionic bond is the result of ___________?
Electrostatic force of attraction between the opposite charges of these ions.
What are not shared in ionic bonds?
Electrons
What must occur before ionic bonding takes place?
The difference in elecctronegativity must be gre3ater than 1.7 on the pauling scale.
Ionic bonds are usually formed between what type of atoms?
Metals and nonmetals
How can you determine whether a compound will form an ionic bond, equation wise?
Difference in electronegativity values (/\EN)
What are three ionic bond examples?
Cesium chloride
Potassium Iodide
Sodium Fluoride
What are the common ionic compound characteristic physical properties?
High melting and boiling points
Dissolve in water and other polar solvents
In the molten or aqueous state good conductors of electricity
Form crystalline lattice with repeating positive and negative ions
Why does the formation of ionic compounds create such attractive force?
The attractive forces between the oppositely charged ions are maximized
Repulsive forces between ions of like charge are minimized
What type of atoms form covalent bonds?
Atoms with similar electronegativities
Why don’t atoms with similar electronegativities form ions when bonded?
The energy required to form ions through the complete transfer of one or more electrons is greater than the energy that would be released upon the formation of an ionic bond. So it is energetically unfavorable to create ions.
What do covalent bonds contain?
Discrete molecular units with relatively weak intermolecular interactions.
Covalent bonds tend to have what?
Lower melting and boiling points
Covalent bonds are ________________ because ____________?
Poor conductors of electricity in the liquid state because they do not break down constituent ions.
What is it called when atoms share one, two, or three electrons?
Joined by
Single
Double or
Triple covalent bonds
What is the bond order?
The number of shared elecctron pairs between two atoms
What is the bond order for a single, double and triple bond?
Single: 1
Double: 2
Triple: 3
What are the three characteristics of a covalent bond?
Bond Length
Bond Energy
Polarity
What is bond length?
The average distance between the two nuclei of atoms in a bond.
As the nuber of electron pairs increases, bond length _______.
Decreases due to the two atoms being pulled closer together
What is bond energy?
The energy required to break a bond by separating its components into their isolated, gaseous atomic states.
The greather the number of pairs of electrons the ________ energy required to break them.
More
Which has a greater bond energy: single ro triple bond?
Triple
When does polarity occur?
When two atoms have a relative difference in electronegativities
Atoms with higher electronegativity get _______ share of __________.
Larger share of the electron density
What must be negotiated in a covalent bond?
Atoms must negotiate the degree to which the electron pairs are shared
What does a polar bond create?
A dipole
The ________ end of the dipole at the _________ and _____________ end at the __________.
Positive end of the dipole at the less electronegative atom and the negative end at the more electronegative atom
What is a non-polar covalent bond?
Atoms that have identical or nearly identical electronegativities and share electron pairs. They do so with equal distribution of the electrons.
There is no ________ in a non polar covalent bond?
Separation of charge across the bond
Only bond between _____________ will have exactly the same ___________.
Atoms of the same element willl have the exact same electronegativity
What are the seven common diatonic molecules?
H2 N2 O2 F2 Cl2 Br2 I2
When are bonds basically nonpolar?
Difference in electronegativity less than 0.5
Atoms that differ moderately in their electronegativities will result in ____________.
Polar covalent bonds
What is the range of difference in electronegatvities that result in polar covalent bonds?
0.5-1.7
The more electronegative the element the more ____________, taking on a ____________ charge.
Greater portion of the electron density taking on a partial negative charge.
The less electronegative the ___________, taking on a ________ charge.
Smaller portion of the electron density taking on a partial positive charge
How do you indicate the differece in charge?
An arrow crossed at its tail end and pointing toward the negative end.
What is the dipole moment?
A vector quantity give by the equation: p=qd
What do the letters represent in the dipole moment equation?
p: the dipole moment
q: magnitude of charge
d: the displacement vector separating the two partial charges
How is the dipole moment vector measured?
Debye units (Coulomb-meters)
What is a coordinate covalent bond?
Both of the shared electrons originated on the same atom.
What does it generally mean to have a coordinate covalent bond?
A lone pair of one atom attacked another atom with an unhybridized p-orbital to form a bond.
A distinction between where a coordinate bond comes from is only helpful, how?
For keeping track of the valence electrons and formal charges.
Where are coordinate covalent bonds typically found?
In Lewis acid-base reactions