Bonding
Polyatomic ions
2 or more CHARGED particles COVALENTLY BOUND
What is fluorine's electronegativity?
4.0 - it is the highest of all elements
What is electricity
A form of energy associated with the movement of charged particles
What does the delocalized electron act as?
A glue that cements the metal ions in place, the GREATER the number of delocalized electrons, the STRONGER the 'cement'
How does "dry cleaning" work?
A liquid solvent whose forces of attraction are similar to those of oil and dirt are used. The solvents are nonpolar, so unlike water, they dissolve oil
Dipole
A polar molecule
What is a crystal?
A solid which possesses an orderly, internal repeating pattern of structure for the atoms, ions, or molecules that make it up
Examples of polar molecules
ACID, sugar, NH₃, alcohol, water, salt*
Substances that dissociate
ACIDS, NH₃, weak molecular bases
Intermolecular forces of attraction (IMFA)
Also known as Van der Waal forces, these are NOT CHEMICAL BONDS; therefore, they are very weak (5% the strength of a chemical bond)
Types of covalent solids
Amorphous solids, molecular crystals/solids, and network solids
What is "dry cleaning"?
An alternate to cleaning clothes which could be damaged by water and normal detergents
What will heat do to metal's electrical conductivity?
Decreasing the temp will increase the conductivity. This is because it slows down the vibrating cations, which equates to less interference/resistance for the electron's movement.
The strength of the metallic bond and the hardness of the metal is ____________ to the number of delocalized electrons contributed by each atom
Directly proportional
What determines the strength of Van der Waal forces?
Directly proportional to polarity of the molecule and molecular size
Why do metals have high melting and boiling point?
Due to the strength of the metallic bonds; to melt a metal, one must provide to partially overcome the chemical bond, and to boil a metal, once has to completely overcome the chemical bonds (A.K.A. metals have extremely strong cohesive forces)
How to identify covalent bonds
Electronegativity difference less than 1.8 and ALL acids.
Delocalized sea of electrons
Electrons capable of moving from one positive metal ion to another positive metal ion to another within the metal; i.e. they are not restricted to just a single pair of atoms involved in the bonding. It is comprised of valence electrons of the metal atoms, and in some cases, the d electrons of the second-most outer energy level
Ionic bond
Electrostatic (opposite charges) attraction that exists between ions that were formed as a result of a transfer of electrons
Forbidden zone
Energy gap that must be jumped to overcome the energy difference between the outermost energy level and the higher energy levels
Coulomb's Law
F = k |q₁q₂|/r² where F is the force of attraction, k is a proportionality constant, q is the charge of an ion, and r is the internuclear distance between the two ions
What is needed for good electrical conductivity?
Flow of charged particles (A.K.A. flow of electrons)
What is resistance?
Friction-like force that opposes the flow of electrons within a conductor (?). It causes electrical energy to be lost in the from of heat
Metal's electrical conductivity
Good; flow of charged particles is the flow of delocalize electrons through the conduction bands from one ion to the next. Metals with less delocalize electrons are better conductors of electricity because they have less electrical resistance
Metal's thermal conductivity
Good; metallic bonds allow the positive metal ions enough freedom of movement that they can pass on KE through vibration, and the delocalize electrons can transfer KE through collision. Metals with fewer delocalized electrons are better thermal conductors because they have more freedom of movement (weaker "cement")
Enthalpy
H, the heat content of a substance; very loosely, this means it is a measure of all the KE and PE for a substance. It is impossible to measure absolute enthalpies.
Strong acids
HCl, HNO₃, H₂SO₄
As bond order _________, bond energy _______
Increases; increases
As bond order _________, the additional electron density between the two atoms' nuclei _______
Increases; increases
As bond order __________, the amount of space occupied by the bonding electrons ______
Increases; increases
What determines the strength of a SINGLE covalent bond
It is DIRECTLY PROPORTIONAL to the polarity of the bond and INVERSELY PROPORTIONAL to the distance separating the atoms
What is the purpose of the crystalline form of metal?
It minimizes cation-cation repulsion and maximizes attraction between cations and delocalize electrons, which all provide for greater stability
What is the structure of soap
Long, nonpolar, hydrocarbon "tail" with polar "head"
Amorphous solids
Made of large, irregularly shaped molecules arranged in a random pattern, held together by Van der Waal forces. Vary in terms of brittleness and hardness; tend to be soft compared to metallic and ionic bound substances. HAVE MELTING POINT RANGES due to varying forces of attraction between the molecules due to the irregular shape. Ex wax, glass, most plastic, tar, rubber
Molecular crystal/solid
Made of molecules arranged in a crystalline lattice, held together by Van der Waal forces. Brittle and tend to be softer than ionic or metallic substances. Ex ice, dry ice, moth balls, sugar
Superconductors
Material which conducts electricity with no resistance
What is the purpose of the shape of the crystal lattice?
Maximize attraction and minimize repulsion
Metalloids forbidden zone
Medium-sized; can conduct electricity, but only under special circumstances (specifically energy), hence the same "semi-conductors"
How to tell something is metallically bound
Metal substances bound to another metal substance
Types of chemical bonds
Metallic, ionic, covalent
Nonpolar molecule
Molecule that posseses an even distribution of charge
Polar molecule
Molecule that posseses an uneven distribution of charge
Molecules
NEUTRAL particles constructed of COVALENTLY BOUND atoms
The strength of a bond is _______________ of its surroundings
NOT INDEPENDENT; atoms at or near the bonding site influence the bond energy
Anion
Negatively charged ion
Non-spontaneous reactions
Occurs with you getting involved. Enthalpy = positive, entropy = negative
Spontaneous reactions
Occurs without you getting involved. Enthalpy = negative, entropy = positive. It is more likely to an exothermic reaction because this will result in products lower in energy than the reactants, which will make it more stable (lower energy = more stable: all things in nature seek stability)
Superconductivity
Phenomena displayed by some metals at extremely low temperatures; near absolute zero
How to tell something is ionically bound
Polyatomic ion bound to another substance EXCEPT acids, group I or II bound to BrONClIF, and an electronegativity difference of 1.8 or greater. The two atoms must be extreme opposites of one another
Ionic substances electrical conductivity
Poor, unless it is in a molten state; unlike metals ionic substances do not posses delocalized electrons, so there is no flow of charged particles. The only way for there to be a flow of charged particles is if the ions were able to flow, which only occurs in a molten state or when it is dissolved in an aqueous solution (dissociation). However, it is not as effective as metal's flowing, delocalized electrons
Covalent substances electrical conductivity
Poor; the vast majority of covalently bound substances do not dissociate into ions when dissolved. The one exception is acids (strong dissociate 100%; weak only 5%) and weak molecular bases (ex. NH3)
Ionic substances thermal conductivity
Poor; they have proximity but little/no freedom of movement
Cation
Positively charged ion
What is needed for good thermal conductivity?
Proximity (of the particles) and freedom of movement/motion/vibration; able to pass of KE from one particle to the next with relative ease
Entropy
S, measure of disorder within a system
Conduction band
Set of higher energy levels to which the valence and d electrons jump to
Covalent bond
Sharing of a pair of electrons. The binding force results from the attraction between these shared electrons and the positively charged nuclei of the atoms entering into the bond (overlap of energy levels - one orbital swells to overlap w/an orbital of another atom) It is represented by a dash. Atoms below row 2 are too large to allow for the sharing of electrons
Pure covalent bond
Sharing of electrons is essentially equal; electronegativity difference is less than or equal to .4
Polar covalent bond
Sharing of electrons is unequal; electronegativity difference is between .4 and 1.8 (partial charges are assigned) ACIDS ARE ALWAYS POLAR
Formula unit
Simple whole number ratio among the ions in an ionic (or metallic) structure; used to express ions found in a crystal lattice
Network solids
Sometimes called covalent crystals, they are the rarest and made up of atoms and held together by COVALENT BONDS, not Van der Waal forces. Therefore, one could argue the entire crystal structure is one giant molecule. Typically very hard and brittle, have high melting and boiling points. Ex diamonds and quartz
Acid's electrical conductivity
Strong acids dissociate 100% when dissolved in water. Weak acids only dissociate about 5% (most remain in molecular form), therefore it conducts electricity to a lesser extent. Also, most covalently bound substances to not posses delocalized electrons capable of traveling through a material EXCEPT for graphite
Emulsion
Temporary mixture of two or more immiscible substances
What determines the shape of the crystal lattice?
The #cation to #anions ratio (i.e. the charges of the ions) AND the radius of the cation to the radius of the anion ratio (i.e. the size of the ions)
Bond energy
The amount of energy required to separate ONE mole's worth of two atoms, chemically bound together (AKA bond), into two electrically neutral particles; it is usually the AVERAGE bond energy
Lattice energy
The amount of energy that would be released by the imaginary process in which isolated particles of a substance (atoms, ions, or molecules) come together to form one mol of crystalline substance. The greater the force of attraction, the greater the lattice energy. Must be determined from experimental data
Bond length
The average distance between the nuclei at the point where attractive and repulsive forces are dominant; the atoms are in their most stable state, resulting in the maximum release of energy
Dissociation
The breaking apart of neutral substance in solution into positively and negatively charged ions
Bond order
The number of pairs of electrons shared between two atoms (ex. bond order 1 = single pair of electrons shared/single bond; bond order 2 - two pairs of electrons being shared/double bond, ect).
What determines the polarity of a dipole?
The polarity of a dipole is DIRECTLY PROPORTIONAL to the magnitude of the NET partial charges and to the distance separating these NET partial charges. Usually, the magnitude of the net partial charges tend to be the dominant factor in determining polarity
What is a crystalline lattice?
The structure of a crystal; means that the surface of a metal is very regular, so photons not absorbed are reflected at distinct angles (a rough surface would scatter light; even reflection is necessary for luster)
Thermodynamics
The study of energy changes; tell whether a reaction is spontaneous or not
Kinetics
The study of reaction rates
Electronegativity
The tendency of an atom to attract electrons to itself, while bound to another atom
What determines the solubility of substances in other substances
The type of Van der Waal forces; "Like dissolves like" The closer the two substances are to one another in terms of the type of Van der Waal forces, the greater the solubility of one in the other
What is the relationship between thermodynamics and kinetics?
There is NO RELATIONSHIP
How do incandescent lightbulbs work?
There is a very thin wire inside the bulb called a filament. Electricity is forced to pass through this filament, and due to electrical resistance the filament heats up to the point of giving off light
Why are metalloids so important?
They are a key component in any electronic equipment; essential for making transistors and computer chips. Usually the transistors consist of Group IV metalloid that has been doped with Group III or Group V element
How does soap/detergent work?
They work by acting as emulsifying agents. The hydrophobic tails, which are nonpolar, are attracted to the nonpolar dirt and grime. So, the nonpolar tails surround the dirt/grease particles, forming a micelle. What is left is polar heads, which is attracted to water, sticking out of the nonpolar dirt/grime. So, when rinsing, water attaches to the polar heads of the soap and carries off the dirt/grime
What hold covalently bound substances together?
Van der Waal forces; because of this, the melting and boiling points tend to be much lower than those of ionic or metallic substances
Covalent substances thermal conductivity
Varies; if molecules are in close proximity to one another and have a sufficient degree of freedom of movement/vibration, then the substance is a good conductor of heat (gases fail to meet the first requirement and some solids fail to meet the second)
Nonmetals forbidden zone
Very large and extremely hard for electrons to make the jump
Metal's forbidden zone
Very small, and easy for electrons to make the jump
Metallic bonds
Very strong and holds metals together; involves positive metal ions held together by a mutual attraction for a "sea of electrons" which surround the metal ions
Examples of nonpolar molecules
Wax, oil, grime, gasoline, fat, most gases, HYDROCARBONS
When do we see gold?
When all light except violet is reflected at the same angle it came down
Why are ionic substances brittle?
When hit by a strong force, they shatter along planes between rows of ions due to repulsive forces becoming dominant
When do we see white?
When light is reflected and hits the eye from all directions
When do we see silver?
When light is reflected at the same angle it came down; it is a true reflection
What allows metals to be malleable and ductile?
the crystalline form; when force is applied, the cations simply "slide" over one another along a cushion of delocalize electrons
Formula to approximate the heat of a rxn
∆H = −∑(bond energies of products) + ∑(bond energies of reactants) ; neg sign indicates and exothermic rxn and a pos sign indicates an endothermic rxn. The answers are only an APPROXIMATION
