Chemical Bonding Flashcards
What is a compound?
A substance that is made from two or more different elements combined together chemically.
What is the octet rule?
When bonding occurs, atoms tend to reach an electron arrangement with eight electrons in their outermost energy level.
What is an ion?
Charged atom or group of atoms.
What is an ionic bond?
The force of attraction between oppositely charged ions in a compound. Ionic bonds are always formed by the complete transfer of electrons from one atom to another.
What is the hydroxide ion?
OH-
What is the Nitrate ion?
NO3-
What is the hydrogencarbonate ion
HCO3-
What is the permanganate ion?
MnO4-
Carbonate ion
CO3–
Chromate ion
CrO4–
Dichromate ion
Cr2O7–
Sulfate ion
SO4–
Sulfite ion
SO3–
Thiosulfate ion
S2O3–
Phosphate ion
PO4—
Ammonium ion
NH4+
What are the characteristics of transition metals?
- They have variable valency
- Usually form coloured compounds
- Widely used as catalysts.
What are transition metals?
One that forms at least one ion with a partially filled sublevel
What are molecules?
A group of atoms joined together. It is the smallest particle of an element or compound that can exist independently.
What is valency?
Valency of an element is defined as the number of atoms of hydrogen or any other monovalent element with which each atom of the element combines.
What is a sigma bond?
Formed by the head on overlap of two orbitals, single bonds are always sigma bonds.
What is a pi bond?
Formed by the sideways overlap of p orbitals.
Single, double and triple bonds
Single bonds are always sigma bonds, double bonds are always 1 sigma and 1 pi bonds and triple bonds are always 1 sigma bond and 2 pi bonds
What are the properties of ionic compounds?
- Contain a network of ions in the crystal
- Usually hard and brittle
- Have high melting points and boiling points
- Usually solid at room temperature
- Conduct electricity in molten state or when dissolved in water.
What are the properties of Covalent Compounds?
- Contain individual molecules
- Usually soft
- Have low melting and boiling points
- Usually liquids, gases or soft solids at room temperature.
- Do not conduct electricity
What does VSEPR stand for?
Valence Shell Electron Pair Repulsion Theory
What is VSEPR?
This theory states that the shape of a molecule depends on the number of pairs of electrons around the central atom. Lone pair/Lone pair>bond pair/lone pair>bond pair/bond pair.
What is Electronegativity?
The relative attraction that an atom in a molecule has for a shared pair of electrons in a covalent bond.
What is a polar covalent bond?
A bond in which there is unequal sharing of the pair(or pairs) of electrons. This causes one end of the bond to be slightly positive(S+) and the other end slightly negative(S-)
What is pure covalent?
A covalent bond where there is an equal sharing of the two electrons in the bond.
What are the main uses of electronegativity values?
- To predict the polarity of covalent bonds
- To predict which compounds are ionic and which are covalent.
Polarity
0-0.3 - Non polar
0.3-1.7 - Polar covalent
0.3 - 1.0 - Polar covalent
1.0 - 1.7 - Highly polar covalent
Greater than or equal to 1.7 - Ionic bond
Why are there some molecules, which even though they are polar covalent, are non polar?
Since the centre of the partial negative charges coincides with that of the partial positive charges, non of these molecules are polar.
What molecules are non polar even though they are polar?
BCl3, CO2, CCl4
What is intramolecular bonding?
Bonding within or inside molecules. (Ionic, Covalent)
What is intermolecular bonding?
Bonding that takes place between molecules( Van Der Waal, dipole-dipole, hydrogen bonding)
What are Van Der Waal Forces?
Weak attractive forces between molecules resulting from the formation of temporary dipoles. They are the only forces of attraction between non-polar molecules. The bigger the molecule the stronger the Van Der Waal force, this means a higher boiling point.l
What are dipole-dipole forces?
Forces of attraction between the negative pole of one polar molecule and the positive pole of another molecule.
What are hydrogen bonds?
Particular types of dipole-dipole attractions between molecules in which hydrogen atoms are bonded to nitrogen, oxygen or fluorine. The hydrogen atom carries a partial positive charge and is attracted to the electronegative atom in another molecule. Thus, the hydrogen bond acts as a bridge between two electronegative atoms in separate molecules. Stronger than Van Der Waal and dipole-dipole but weaker than covalent.
