2.2.2 structure and bonding Flashcards
an ionic bond is…
a strong electrostatic force of attraction between oppositely charged ions
state and describe the structure of ionic compounds
giant ionic lattice where the positive ions attract the negative ions and are surrounded by them and vice versa
state and explain whether ionic compounds have a high or low melting and boiling points
high, the attraction between ions is very strong which means lots of energy is needed to overcome this force
state and explain the conduction of ionic compounds in both solid and liquid states
when solid there are no free ions to conduct electricity so the compound is a poor conductor
when molten the ions are free to move and conduct electricity so the compound is a good conductor
a covalent bond is…
a shared pair of electrons (the strong electrostatic force of attraction between a shared pair of electrons and the nuclei of the bonded atoms)
a dative covalent bond is…
formed when the shared pair of electrons in a covalent bond come from only one of the bonding atoms
a dative covalent bond could also be called…
co-ordinate bonding
give the names of the two covalent structures
giant covalent / macromolecular
simple molecular
describe the simple molecular structure
individual molecules with weak forces between them with atoms being joined by covalent bonds
state and explain wether simple molecular substances have a high or low melting and boiling points
low, there are weak London forces between molecules that need little energy to overcome
describe a giant covalent structure
lattice structure in which all atoms are joined to others by covalent bonds
state and explain whether simple molecular substances are good or poor conductors
poor, there are no free electrons to move and conduct electricity
state and explain whether giant covalent substances have high or low melting and boiling points
high, strong covalent bonds need lots of energy to overcome
state and explain whether giant covalent substances are poor or good conductors
poor, in most giant covalent substances there are no free electrons that can move and conduct electricity except in graphite where there are 3 carbon to carbon bonds with each 4th outer electron being able to move and conduct electricity
explain why graphite is malleable
graphite is formed in layers that are able to slide over each other easily
a metallic bond is…
the electrostatic force of attraction between positive metal ions and a sea of delocalised electrons
state and describe the structure of metallic substances
giant metallic, lattice structure of metal ions with outer shell electrons free to move through structure
state and explain whether metallic substances have high or low melting and boiling points
high, there is strong electrostatic force of attraction between the positive metal ions and sea of delocalised electrons that means lots of energy is needed to overcome this
state and explain whether metallic substances are poor or good conductors
good, the sea of delocalised electrons are free to move through the structure and conduct electricity
explain why metallic substances are malleable
the positive ions are all identical and formed in layers that allow the ions to slide easily over one and other
from highest to lowest order the following by their repulsion
• lone pair to bond pair
• bond pair to bond pair
• lone pair to lone pair
highest
lone pair to lone pair
lone pair to bond pair
bond pair to bond pair
lowesteach lone pair reduces the bond angle by…
2.5°
name the shape of a molecule with 2 bond pairs and 0 lone pairs and give the bond angle
linear 180°
name the shape of a molecule with 3 bond pairs and 0 lone pairs and give the bond angle
trigonal planar 120°
name the shape of a molecule with 4 bond pairs and 0 lone pairs and give the bond angle
tetrahedral 109.5°
name the shape of a molecule with 3 bond pairs and 1 lone pair and give the bond angle
trigonal pyramidal 107°
name the shape of a molecule with 2 bond pairs and 2 lone pairs and give the bond angle
bent 104.5°
name the shape of a molecule with 5 bond pairs and 0 lone pairs and give the bond angle
trigonal bypyramidal 120° & 90°
name the shape of a molecule with 6 bond pairs and 0 lone pairs and give the bond angle
octahedral 90°
name the shape of a molecule with 2 bond pairs and 1 lone pair and give the bond angle
bent 118°-119°
name the shape of a molecule with 4 bond pairs and 1 lone pair and give the bond angle
distorted 89° & 119°
name the shape of a molecule with 3 bond pairs and 2 lone pairs and give the bond angle
t-shaped 89°
name the shape of a molecule with 2 bond pairs and 3 lone pairs and give the bond angle
linear 180°
name the shape of a molecule with 5 bond pairs and 1 lone pair and give the bond angle
square pyramidal 89° & 90°
name the shape of a molecule with 4 bond pairs and 2 lone pairs and give the bond angle
square planar 90°
give the workings out for how to work out the shape
group of central atom + no. of atoms around central atom = x
x + charge of compound = y
y / 2 = z
z - no. of atoms around central atom = no. of lone pairs
give the four elements that are exceptions when trying to find out the shape of a compound
when combined with oxygen nitrogen, carbon, sulphur and chlorine will need to be drawn via dot and cross diagram to work out the shape
electronegativity is …
the relative tendency of an atom in a covalent bone in a molecule to attract electrons in a covalent bond to itself
name two reasons electronegativity increases or decreases and explain why
- number of protons increase so atomic radius increases and electrons in the same shell are pulled in more
- decreases down the group as distance between the nucleus and outer electrons so shielding of inner shell electrons increases
name the four most electronegative atoms from lowest to highest
N & Cl
O
F
name the three types of intermolecular force
- induced dipole-dipole / london force
- permanent dipole-dipole
- hydrogen bonding
explain why induced dipole-dipole is formed
• electrons are moving constantly and randomly causing electron density to fluctuate and some of the molecules to become more or less negative to form dipoles that can cause dipoles to form in neighbouring molecules
explain the effect of increasing electrons on boiling points
the more electrons the higher the chance temporary dipoles will form so the induced dipole-dipole interactions are stronger between molecules so boiling point increases
how do you predict the bond angle of C, S, N and Cl with oxygen
draw a dot and cross diagram
