Chapter 3- Covalent Substances Flashcards
why do non-metallic atoms tend to share electrons
they have a relatively high number of electrons in their outer shells
what are intramolecular bonds
bonds within a molecule
what is the octet rule
many atoms become more stable if they get an outer shell of 8 electrons
what is covalent bonding
the sharing of electrons between atoms
what boiling do non-metallic elements and compounds have
low
can non-metallic elements and compounds conduct electricity
No
Why dont molecular substances conduct electricity
because they dont contain free moving charged particles
are intermolecular bonds strong
no hence why they break
are intramolecular bonds strong
yes hence why they hold
what is a single covalent bond
when atoms share two electrons. one from each atom.
what is the molecular formula
an indicator of the number and types of atoms found in a molecule
what are electrons involved in the covalent bond called
a shared pair
what are electrons that are not involved in the covalent bond called
lone pairs
what is a double covalent bond
two pairs of electrons are shared between atoms
what are triple covalent bonds
when 3 electron pairs are shared between 2 atoms
what does a diatomic molecule contain
2 atoms
what is a polyatomic molecule
molecules made up of 2 or more atoms
What is the VSEPR theory
a way of predicting the shapes of small molecules
How does the VSEPR theory work
the pairs of electrons present in the valence shell will repel each other and try to get as far away from each other as possible
Do lone pairs influence the shape of a molecule
Yes but they are not considered a part of the shape
What key factor determines the electrons distribution in a diatomic molecule
electronegativity
what makes a bond non-polar
if the bond have an equal distribution of electronegativities as there is no charge on either end of the bond
what atom has the stronger pull in a covalent bond of 2 different elements
the atom that is the most electronegative
in a molecule, which element has a partial negative charge
the element with the higher electronegativity
in a molecule, which element has a partial positive charge
the element with the lower electronegativity
what is a permanent dipole
the separation into 2 regions as they have two oppositely charges poles at each end of the molecule
how do you determine if a molecule is polar
if the difference of electronegativities is greater than 0.5 but less than 1.7
what is an ionic bond
electrons are transferred to the more electronegative atom, electronegativity difference must be greater than 1.7
what does the polarity of molecules with more than 2 atoms depend on
the shape of a molecule and the polarity of its covalent bonds
what is a symmetrical molecule
(evenly distributed polar bonds) they are non polar and cancel each other out.
what are asymmetrical molecules
(polar bonds) are polar molecules due to a net dipole being created in the molecule
what are the 3 types of intermolecular forces
dispersion forces, dipole-dipole attraction and hydrogen bonding
when does the strength of a dispersion force increase
as the relative molecular mass increases.
Larger molecules = more electrons = more chance of instantaneous dipoles
what is a dispersion force
forces that exist between all molecules whether they are polar or non polar
what are dispersion forces caused by
temporary dipoles in the molecules that are the result of random movement of electrons surrounding the molecule
what is the weakest of all the intermolecular forces
dispersion forces
what is the strongest of all the intermolecular forces
hydrogen bonding
what is dipole-dipole bonding
the attraction of dipoles to each other (polar bonds when the partial positive ends of one molecule will be attracted to the partial negative ends of another molecule)
when does the strength of a dipole-dipole attraction increase
with increased polarity
what is hydrogen bonding
occurs between molecules where hydrogen is bonded to nitrogen, fluorine or oxygen. a non-bonding pair of electrons on the N,O or F atoms of neighboring molecules.
what are allotropes
different structural arrangements of the same element
what are the allotropes of carbon
graphite and diamond
what is the structure of diamond
covalent network lattice
why is diamond strong
their are no weak intermolecular forces present
what are the properties of diamond
high melting point and sublimation point, does not conduct electricity
what is the structure of graphite
covalent layer lattice
what are amorphous forms of carbon
charcoal and carbon black. both have no consistent structure
