Bonding - Part 1 Flashcards
Electronegativity
Ability of an atom to
attract a bonding pair of electrons in a covalent bond
towards itself
Elements that are highly electronegative?
Oxygen and Fluorine
Dipole
a pair of equal and oppositely charged poles
separated by a distance.
Explanation if electrons are shared equally in a compound?
Produces a NON-POLAR covalent bond.
Purely covalent character.
(electronegativity difference between the two atoms is minimal. Eg H—H
Explanation if electrons are unequally shared in a compound?
Produces a POLAR covalent bond.
Covalent bond with a little bit of ionic character Eg. H—F
(large electronegativity difference - between two atoms is between 0.4 to 2.0 then electrons are unequally shared as one atom pulls electrons more strongly, forming a dipole)
Explanation when an electron is transferred from one atom to another?
Occurs if large difference in electronegativity between two atoms (eg. Between 2 and 4)
Forms an ionic bond
Exist as separate ions, no distortion of electron cloud
Explain the bonding in carbon dioxide?
O=C=O
Symmetrical shape cancels out dipole with otherwise would form between C and O
Explain this bond H—F?
The difference in the electro negativity of the two atoms causes a dipole.
polar covalent bond
partial ionic character
Isoelectronic ions
Ions which have the same electron configuration. (Number of electrons)
Why does atomic radius decrease from N to Al (or down a group of isoelectronic ions)
Atomic number increases
Nuclear charge increases
Number of shells and electrons stays same
Greater electrostatic attraction between outer shell electron and nucleus
Smaller ionic radius
Two things that are evidence for the existence of ions?
1) The MPs of group 1 chlorides decrease down the group. This is because there are more shells and electrons so a larger atomic radius so a weaker attraction so less energy is required to break the ionic bonds.
2) Electrolysis provides evidence because The migration of coloured ions towards the respective electrodes and the coloured elements formed at each electrode proves the existence of separate ions.
What does a higher ionic charge mean?
Stronger ionic bond
Eg. Na5+ has lost 5 electrons
Larger positive charge
OR COULD U SAY: lost more shells which decreases the ionic radius so the distance between the two attracting ions is smaller so the bond is stronger. ???????¿¿¿
How does ionic radius relate to strength of ionic bond?
larger ionic radius
weaker ionic bond
because the more distance between the two attracting ions.
Typically it is the ionic radius of the cat ion (+) that has an effect on the strength of the bond. Why???????????
Non-polar definition
Electrons are evenly distributed so that no separate positive or negative poles form.
Polar definition
Electrons are unevenly distributed so separate negative and positive poles form.
Dative covalent bond definition
A covalent bond when the shared pair of electrons come from only one of the bonding atoms.
Eg. Ammonium ion, usually ammonia has a lone pair of electrons on its nitrogen
In the ammonium ion the nitrogen provides both of its lone electrons to hydrogen ion to form the dative covalent bond.
Why does the size of isoelectronic ions decrease
across a period of isoelectronic ions
number of electrons stays the same
number of protons in the nucleus increases (atomic number)
stronger attraction between the electrons and the protons in the nucleus
ionic radius decreases
ionic bond
electrostatic attraction between two oppositely charged ions
covalent bond
electrostatic attraction between positive nuclei of the atoms and their shared pair of electrons
What happens to the size of isoelectronic ions across a period?
they decrease
what happens to the size of ionic radius as you go down the group?
it increases because as you go down because you are adding more shells filled with electrons which all repel each other
(and maybe because all ions have the same charge so as shells increase there is a weaker attraction between the protons in the nucleus and their electrons)
Why is there a big jump up in ionic radius as you go from 3+ ions (group 3) to 3- ions (group 5)?
because a whole layer of electrons is added.
eg. these ions are in period 3:
Al 3+ = 10 electrons (2,8)
P 3- = 18 electrons (2,8,8)
Migration of ions example in U shaped drying tube
CuCrO4 (copper chromate)
blue colour of Cu2+ ions migrates to negative electrode
yellow colour of CrO4 2- ions migrates to the positive electrode
Migration of ions example on moist filter paper example
drop of purple potassium manganate solution on moist filter paper placed on microscopic slide.
Ends of the slide are connected to 24 V DC power supply.
After ten minutes the purple colour of the
MnO4 - ion migrates to positive electrode
