Unit 1: Section 3- Bonding Flashcards
Define ionic bonding
Ionic bonding is the electrostatic force of attraction between oppositely charged ions formed by electron transfer
What type of ion does a metal form?
positive
What type of ion does a non metal form?
negative
What structure do ionic crystals have?
giant lattice of ions
How does the size of the ions affect the properties of the bond?
ionic bonding is stronger and the melting points higher when the ions are smaller
How can the charges affect the strength of the ionic bond?
if the charges are higher, the ionic bonds are stronger
Explain why negative ions formed in group 5 to 7 are larger
the negative ion has more electrons than the corresponding atom but the same number of protons, so the pull of the nucleus is shared over more electrons, and the attraction per electron and the attraction per electron is less, making the ion bigger
What happens to ionic radii size going down a group?
it increases, because there are more shells of electrons
What is a covalent bond?
shared pair of electrons
What is a dative covalent bond?
when the shared pair of electrons comes from only one of the bonding atoms
What is metallic bonding?
metallic bonding is the electrostatic force of attraction between the positive metal atoms and delocalised electrons
Name three things that effect the strength of a metallic bond
- number of protons (strength of nuclear attraction)
- number of delocalised electrons
- size of the ions
What is the structure of ionic bonded molecules?
giant ionic lattice
What is the structure of molecules that are covalently bonded?
simple molecular: (Van der Waals forces, permanent dipoles, hydrogen bonds)
macromolecular: giant molecular structures
What is the structure of molecules that are metallically bonded?
giant molecular lattice
What words do you use to describe simple molecular substances?
molecules
intermolecular forces
State the solubility in water of ionic, molecular, macromolecular and metallic compounds
Generally good
generally poor
insoluble
insoluble
State how conductive when solid ionic, molecular, macromolecular and metallic compounds are
poor
poor
poor
good
State how conductive when molten ionic, molecular, macromolecular and metallic compounds are
good
poor
poor
good
State the BP and MPs of ionic, molecular, macromolecular and metallic compounds
high
low
high
high
Describe a linear molecule
2 bonding pairs
0 lone pairs
bond angle- 180
Name three examples of linear molecules
CO2 CS2 HCN
Describe a trigonal planar molecule
3 bonding pairs
0 lone pairs
bond angle- 120
Name 3 examples of trigonal planar molecules
BF3
AlCl3
SO3
Describe a tetrahedral molecule
4 bonding pairs
0 lone pairs
bond angle- 109.5
Name two examples of tetrahedral molecules
SiCl4, SO4 2-
Describe a trigonal pyramidal molecule
3 bonding pairs
1 lone pair
bond angle- 107
Describe a bent molecule
2 bonding pairs
2 lone pairs
bond angle- 104.5
Describe a trigonal bipyramidal molecule
5 bonding pairs
0 lone pairs
bond angle- 120 and 90
Describe an octahedral molecule
6 bonding pairs
0 lone pairs
bond angle- 90
Explain which repels more: lone pairs or bonding pairs
lone pairs- by about 2.5 degrees more per lone pair
Define electronegativity
the relative tendency of an atom in a covalent bond in a molecule to attract electrons in a covalent bond to itself
How is electronegativity measured?
Pauling scale (1-4)
What are the most electronegative elements?
fluorine, oxygen, nitrogen, chlorine
Describe the trend in electronegativity along a period
increases
as the number of protons increases and the atomic radius decreases because the electrons in the same shell are pulled in more
Describe the trend in electronegativity down a group
it decreases down a group because the distance between the nucleus and the outer electrons increases and the shielding of inner shell electrons increases
What type of bonding will a compound have if it contains elements of a similar electronegativity?
purely covalent
What type of bonding will a compound have if it contains elements with a large electronegativity difference?
ionic
When does a polar covalent bond form?
when the elements in the bond have different electronegativities (0.3-1.7)
What is a polar covalent bond?
a bond where it has an unequal distribution of electrons in the bond and produces a charge separation (dipole ends)
How do you identify a symmetrical molecule?
all bonds identical and no lone pairs of electrons
Can a symmetrical molecule be polar?
no, even if the individual bonds within the molecule are polar
Give an example of a symmetrical molecule
CO2
What molecules do Van der Waals forces occur in?
everything except ionic substances
What are Van der Waals also called?
transient, induced dipole- dipole interactions
How do Van der Waals forces occur in molecules?
the electrons are moving constantly and randomly, so the electron density can fluctuate and parts of the molecule become more or less negative
What is the main factor affecting the size of Van der Waals forces?
the more electrons there are in the molecule the higher the chance that temporary dipoles will form, so stronger Van der Waals forces
How can you explain the increasing boiling points down group 7?
increasing numbers of electrons, bigger molecules, so increasing Van der Waals forces between molecules.
What is the trend in boiling points down group 7?
increasing
How can you explain why I2 is a solid and Cl2 is a gas?
Van der Waals forces
How can increasing boiling points of alkanes be explained?
long, more electrons, stronger Van der Waals
What does the permanent dipole-dipole force occur between?
polar molecules
Which bonds are stronger, dipole-dipole or Van der Waals forces?
permanent dipole- dipole
What type of molecules are polar molecules?
asymmetrical
How do polar molecules form a bond?
the significant difference in electronegativity
How does hydrogen bonding occur?
it occurs in compounds that have hydrogen atom attached to one of the three most electronegative atoms of nitrogen, oxygen and fluorine. which must also have an available lone pair of electrons
What is the strongest type of intermolecular bonding?
hydrogen bonding
Why is the boiling point of H2O so anonamously high?
the hydrogen bonding between the molecules
What can form hydrogen bonds?
alcohols, carboxylic acids, proteins, amides
