Chapter 3 - Covalent Substances Flashcards
Allotrope
Different structural arrangements of the same element. For example, diamond and graphite are both made of carbon, but diamond has a covalent network lattice, whereas graphite has a covalent layer lattice.
Amorphous
A substance that does not have a clearly defined structure. E.g. amorphous carbon.
Asymmetrical Molecule
A molecule that is not symmetrical, meaning that it will be polar if it contains polar bonds. For example: trigonal pyramid and planar shapes.
Covalent Bond
A strong chemical bond between non-metal atoms, created through the sharing of valence electrons. Results in a molecule.
Covalent Lattice
A regular arrangement of atoms joined by covalent bonds.
Covalent Layer Lattice
A lattice (such as graphite) made up of two dimensional layers of atoms, held together by weak dispersion forces. Each atom is bonded to three other atoms. Lustrous, conducts electricity, acts as a lubricant and has a high sublimation point.
Covalent Network Lattice
A covalent lattice with each atom bonded to four other atoms, such as in diamond; hard and have high melting points.
Diamond
An allotrope of carbon formed by a covalent network lattice, with each carbon atom bonded to four other carbon atoms. Is hard, translucent and brittle, with a high melting point. Does not conduct electricity.
Diatomic Molecule
A linear molecule that is only made up of two atoms, such as HCl.
Dipole
A pair of oppositely charged regions around a molecule, represented by the Greek letter δ (delta).
Dipole-Dipole Attraction
An intermolecular force between polar molecules; the electrostatic attraction between the positive and negative dipoles of two molecules.
Dispersion Forces
A weak intermolecular force caused by the creation of an instantaneous dipole.
Double Covalent Bond
A covalent bond in which two pairs of electrons are shared, such as in oxygen. Forms 3 electron domains around each atom.
Electron Domain
A region in which a lone pair or bonding electrons could be found. Non-metals have 4 electron domains in their outer shell.
Graphite
An allotrope of carbon formed by a covalent layer lattice, with each carbon atom bonded to three other carbon atoms. Is lustrous with a high melting point, along with having lubricant properties. Does conduct electricity.
Hydrogen Bond
An intermolecular force between hydrogen and either fluorine, oxygen or nitrogen (FON). The strongest of the intermolecular forces.
Instantaneous Dipole (Temporary Dipole)
The sudden or random creation of a dipole in a non-polar molecule, due to the uneven distribution of electrons.
Intermolecular Force
The weak forces between molecules, such as dispersion, dipole-dipole attraction, or hydrogen bonding.
Intramolecular Bond
The strong covalent bonds within molecules.
Lewis Structure
A diagram consisting of dots or crosses, which illustrates the covalent bonds in a molecule.
Molecule
A group of two or more atoms chemically bound together in a discreet structure. Note: not the same as a lattice!
Non-Bonding Electrons (Lone Pairs)
An electron domain that has been filled by two electrons, meaning that it is (usually) unable to form covalent bonds.
Non-Polar
A molecule that does not have a polar charge, due to electronegativities of its atoms being the same, or it having a symmetrical shape.
Polar
A molecule that has a dipole and therefore a slight electrical charge, due to its atoms having a difference in electronegativity up to 1.7.
Polarity
The strength of the electrical charge in a polar molecule. Atoms with greater differences in electronegativity will have greater polarity.
Polyatomic Molecule
A molecule made up of more than two atoms.
Trigonal Pyramidal (Molecule)
A molecular shape formed by three bonding pairs and one lone pair. For example: ammonia (NH3). Polar.
Sublimation Point
The temperature at which a solid is able to transition directly to a gas, without first becoming a liquid.
Single Covalent Bond
A covalent bond in which one pair of electrons are shared, such as in chlorine. Forms 4 electron domains around each atom.
Symmetrical Molecule
A molecule with equal shape, meaning that it will not become polar, even if it has polar bonds. For example: tetrahedral shapes.
Tetrahedral
A molecular shape formed by four bonding electrons, consisting of four branches extending off of a central point. Not polar.
Trigonal Planar (Molecule)
A molecular shape formed by two single bonds and one double bond (a flat pyramid). Polar.
Triple Covalent Bond
A covalent bond in which three pairs of electrons are shared, such as in nitrogen. Forms 2 electron domains around each atom.
VSEPR Theory
Valence Shell Electron Pair Repulsion theory; an idea stating that electrons in their valence shell repel, and therefore will spread out to reduce repulsion.
Covalent Bonding
Bonding between non-metal atoms, through the sharing of electrons.
Structural Formula
A diagram consisting of lines, which illustrates the covalent bonds in a molecule.
Induced Dipole
A temporary dipole in an atom, caused by an instantaneous dipole attracting or repelling nearby electrons.
