Bonding Flashcards
What is ionic bonding?
the electrostatic force of attraction
between oppositely charged ions formed by electron transfer.
What structure do ionic compounds have?
giant ionian lattice of alternating + and - ions
When is ionic bond stronger and the meltingpoints higher?
when the ions are smaller or have higher charges
What happens to the size of the ionic radi as you go down a group?
it is increases because there are more shells of electrons
When do ions form?
when electrons are transferred between elements that have a large difference in electronegativity (metals and non metals)
Are positive or negative ions smaller?
positive because they have lost electrons
What forces hold the ionic lattice together?
very strong electrostatic forces
What are the properties of ionic bonding?
-very high melting point
-soluble in h20
-electrical insulator when solid
-electrical conductors whenmolten/dissolved
-brittle
Why do ionic bonds have a very high melting point?
strong electrostatic forces between oppositely charged ions
Why are ionic bonds soluble in h20?
h20 is very polar so can disrupt forces between ions and break them up
Why are ionic bonds brittle?
when moved ions are no longer alternately arranged so they repel each other and the lattice breaks
What is covalent bonding?
- the sharing of outer electrons to achieve a full shell
- with electrostatic attraction between the shared electrons and the positive nucleus.
What types of covalent bonds exist?
Single, double, and triple bonds,
What is a dative covalent (coordinate) bond?
- A bond where one atom donates a pair of electrons to another atom
- For example, ammonia (NH₃) donates a lone pair to H⁺.
- formed when an electron deficient atom accepts a lone pair of electrons from an atom with a lone pair of electrons
How is a dative covalent bond represented?
- With an arrow showing the direction of electron donation
- from the donor to the acceptor
What is the structure of graphite?
- consists of hexagonal layers
- each carbon bonded three times, and the fourth electron delocalized.
Why can graphite conduct electricity?
Delocalized electrons can carry charge, enabling conductivity
Why does graphite have a high melting point?
Strong covalent bonds require a lot of energy to break.
Why is graphite slippery and low density?
Weak intermolecular forces between layers allow them to slide, and the layers are far apart compared to covalent bond lengths.
What is the structure of diamond?
Each carbon atom is bonded four times in a tightly packed lattice.
Why is diamond non-conductive?
no free electrons to charge
What are the similarities between diamond and graphite?
- Both have high melting points due to strong covalent bonds
- both insoluble in water because the bonds are too strong to break.
What are the names and bond angles of molecule with no lone pairs?
What are the names and bond angles of molecules WITH lone pairs?
What happens to bond angles with 4 bond pairs and 2 lone pairs?
bond angle remains at 90 as Lone pairs repel equally, so the bond angles remain unchanged.
What is electronegativity?
The ability of an atom to attract electrons in a covalent bond.
What makes a covalent bond polar?
shared pair of electrons are not shared equally
Why is chlorine (Cl₂) nonpolar?
Both atoms have equal electronegativity, so electrons are shared equally, so molecules are symmetrical
Why are hydrocarbons nonpolar?
Electrons are shared equally in C–H bonds, and the molecules are symmetrical
What makes water a polar molecule?
Oxygen is more electronegative than hydrogen, creating uneven charge distribution
Can a molecule with polar bonds be nonpolar?
YES
if the molecule is symmetrical (e.g., CO₂), the dipoles cancel out.
What are van der Waals forces?
Weak intermolecular forces due to temporary dipoles.
How do van der Waals forces form?
- Temporary dipoles arise when electrons unevenly distribute.
- These induce dipoles in neighboring molecules, causing weak attraction.
How does molecular size affect van der Waals forces?
Larger molecules with more electrons have stronger van der Waals forces
What are dipole-dipole forces?
Forces between molecules with permanent dipoles.
How do dipole-dipole interactions compare to van der Waals?
They are STRONGER
What is an instantaneous dipole?
- A temporary dipole created by the random movement of electrons in an atom or molecule
- causes uneven charge distribution at any given moment.
- happens in an instant
What is an induced dipole?
A dipole created when an instantaneous dipole in one molecule induces a dipole in a nearby molecule by attracting or repelling its electrons
What is a Dipole?
a dipole occurs when there is a separation of charge within a molecule due to differences in electronegativity
What is hydrogen bonding?
A strong type of dipole-dipole interaction between hydrogen and highly electronegative atoms like N, O, and F
Which atoms must be present for hydrogen bonding to occur?
Nitrogen (N)
Oxygen (O)
Fluorine (F)
- bonds will form between lone pairs of N, F OR O and a Hd+
Why is ice less dense than liquid water?
- In liquid water, hydrogen bonds constantly break and reform as molecules move about
- In ice, the hydrogen bonds hold the molecules in fixed positions; this makes them slightly further apart than in liquid water
Why does HF have a higher boiling point than HCl?
HF exhibits hydrogen bonding, which is stronger than dipole-dipole forces in HCl.
Do molecules with hydrogen bonding also have other intermolecular forces?
Yes, they also have van der Waals and dipole-dipole forces
What is the importance of hydrogen bonding?
- ice is less dense than water
- water has a much high melting and boiling point than would be expected
- protein folding
- DNA base pairing
Enzyme reactions
What is metallic bonding?
Electrostatic attraction between positive metal ions and delocalized electrons in a metallic lattice
How does the number of delocalized electrons affect metallic bonding?
More delocalized electrons result in stronger bonding and higher melting points
Why are metals good conductors of electricity?
The delocalized electrons can move freely and carry an electrical charge
Why are solid metals insoluble?
The metallic bonds are too strong to be broken by interaction with solvents
Do ionic compounds conduct electricity? why?
Yes
When molten as the ions are free to move and carry charge
what is simple molecular covalent bonding?
- strong covalent bonds between atoms
- weak van der waals forces of attraction between molecules
Are there any lone electrons in simple covalent bonding?
NO
Can simple molecular covalent molecules conduct electricity? why?
NO
all electrons used in boding and aren’t free to move
Do simple molecular substances have a high/low melting point? why?
Low - weak van der waals forces of attraction between molecules that don’t take much energy to overcome
Describe macromolecular covalent bonding
Lattice of many atoms held together by strong covalent bonds
Do metallic compounds conduct electricity? why?
Yes as delocalised electrons can move throughout the metal to carry charge
How does the strength of metallic bonds change across the periodic table?
Why?
- Increases → higher Melting and boiling points, stronger Higher charge on metal ions
- More delocalised electrons per ion
Stronger force of attraction between them
What affects electronegativity
- nuclear charge
- atomic radius
- electron shielding
What is the strongest type of inter-molecular force?
Hydrogen bonding
Are van der waals forces stronger in smaller or larger molecules
Larger - more electrons
describe permanent dipole-dipole attraction
- some molecules with polar bonds have permanent dipoles (forces of attraction between those dipoles and those of neighboring molecules)
What does the electron pair repulsion theory state?
the electron pairs will take up positions as far away from each other as possible to minimise the repulsive forces between them
Which experience the most repulsion?
LP-LP repulsion strongest
LP-BP repulsion middle
BP-BP repulsion weakest
What are the similar structural and bonding features of diamond and graphite
- Both consist of entirely carbon atoms
- Both have covalent bonding
- Both have giant covalent (crystal lattices) structures
What is a giant ionic lattice?
Repeating/ alternating pattern of oppositely charged ions
Why are metals malleable?
Layers can slide over each other
Why is graphite soft?
Weak van der waals forces between its layers
