Structure and Bonding Flashcards
—– tend to lose electrons
Metals
—– tend to gain electrons
Non-metals
Covalent bonding occurs between
Non-metals
Is covalent bonding strong or weak?
Strong
A cation is…
Positive
An anion is…
Negative
In Lewis structures, the least electronegative element goes…
In the center of the molecule (with hydrogen as the exception)
The two factors that determine the shape of a molecule are…
Number of bonds and number of non-bonding electron pairs (the interactions of these regions of negative charges gives the molecule it’s shape)
When one atom involved in a bond has a higher electronegativity than the other…
it attracts the electrons in the bond more strongly, resulting in a dipole (charge imbalance) across the bond.
Dipoles can cancel if…
They are directly across from each other and the sizes of the dipoles are the same (must be same atoms, molecule must be symmetrical)
Intermolecular forces in covalent or molecular substances are…
Weak (caused by weak temporary dipoles, not much energy needed to overcome attraction)
Intramolecular forces in covalent or molecular substances are…
Strong (make up of very strong, high energy covalent bonds, lots of energy needed to break)
Polar solvents can dissolve…
Polar Solutes (bond energies are similar enough to break preexisting forces and create new attractions)
“Heavier” molecules tend to have higher melting point because…
They have more bonds, so more temporary dipoles, so they have more intermolecular force (i.e. more energy needed to overcome)
Ionic substance tend to be hard and brittle because…
Their strong ionic bonds means much force is needed to overcome them (they are hard), and they are brittle because they are directional bonds. If the right kind of force was applied, cations would be directly beside cations, and repulsion would occur.
Covalent network substances are hard because…
They are held together by strong covalent bonds which require a high amount of energy to break.
Metals are malleable because…
The strong metallic bonds that hold together the substance are non-directional. The free electrons and cations can form new attractions when they are moved, so the metal can stay together if the position of the particles change.
Metals are conductive because…
The delocalised electrons can respond to charge imbalances.
moles (n)=
mass (m)/molar mass (M)
What is Enthalpy?
The amount of energy in the bonds of a substance.
If a system give out heat, it is…
Exothermic. Products have a lower energy than before, this energy is lost as heat.
If a system absorbs heat, it is…
Endothermic. Products have more energy than before, this energy is gained as heat.
Bond making is…
Exothermic (bonds=lower energy state)
What is the equation for change in enthalpy?
ΔrH°=Σ(bonds broken)-Σ(bonds made)
