4. Bonding Flashcards
S2.1, S2.2, S2.3
cations
Positive ions formed by metals losing valence electrons.
anions
Negative ions formed by non-metals gaining electrons.
state the factor that determines the number of electrons lost/gained
the electron configuration of the atom
ionic bond
electrostatic attraction between oppositely charged ions
state of most ionic compounds at room temperature
(with lattice structures)
solids
structure of ionic compounds
Giant Ionic Lattice - a repeating 3D structure of negative and posetive ions bonded together by strong electrostatic attraction
melting/boiling point of ionic compounds
high - due to the strong electrostatic attractions between the oppositly charged ions a large amount of energy is needed to overcome these forces
conductivity of ionic compounds
in solid form - does not conduct electricity because the oppositely charged ions are not able to move freely between the positive and negative electrodes and are unable to carry and electrical charge
in a liquid/melted - does conduct electricity because the oppositely charged ions are able to move freely between the positive and negative electrodes and carry an electrical charge
can conduct when in liquid form
state the factors that determines the charge of an ion
the number of electrons the atom needs to lose/gain to achieve a full outer shell
solubility of ionic compounds
many are soluble in water - the energy given out when ions become hydrated (hydration energy) provides the energy to overcome the forces holding the ions together in the lattice (lattice enthalpy)
polyatomic ions
ions containing more than one element
give the names of the polymatic ions:
NH4+, OH-, NO3-, HCO3-, CO3-2, SO4-2, PO4-3
- ammonium NH4+
- hydroxide OH-
- nitrate NO3- (from nitric acid, HNO3)
- hydrogencarbonate HCO3-
- carbonate CO3-2 (from carbonic acid, H2CO3)
- sulfate SO4-2 (from sulfuric acid, H2SO4)
- phosphate PO4-3 (from phosphoric acid H3PO4)
covalent bond
the electrostatic attraction between a shared pair of electrons and the posetively charged nuclei
single, double and triple covalent bond
involve one, two and three shared pairs of electrons respectively
state the relationship between bond length, bond strength and the number of shared electrons
do they increase/decrease
bond length decreases and bond strength increases as the number of shared electrons increases
bond polarity
results from the difference in electronegativities of the bonded atoms
trends in electronegativity values
electronegativity values for each element can be found in section 8 of the IB data booklet
generally, the values increase across a period and decrease down a group
state the factors that determine whether a molecule is polar or not
- relative electronegativities of the atoms in the molecules (bond polarity)
- its shape
how is bond polarity shown
either with partial charges, dipoles or vectors
Lewis (electron dot) structures
dot and cross diagrams
show all the valence electrons in covalently bonded species
“octet rule”
the tendancy of atoms to gain a valence shell with a total of 8 electrons
exceptions to “octet rule”
some atoms, like Be and B, might form stable compounds with incomplete octets of electrons
resonance structures
occur when there is more than one possible position for a double bond in a molecule
how is the charge of an ion related to its position in the periodic table
- element (metals) on the left side of the periodic table form positive ions whilst elements on the righ side (non metals) form negative ions
- the group number indicates the number of valence electrons and how many it needs to lose/gain to have a full outer shell
