Topic 4: Bonding Flashcards
what are exceptions to the octet rule?
- hydrogen
- helium
- beryllium
- Boron
- elements from period 3 onwards
What type of bonding occurs with an electronegativity difference of 0-0.4?
non-polar covalent
What type of bonding occurs with an electronegativity difference of 0.5-1.7?
polar covalent
What type of bonding occurs with an electronegativity difference of ≥1.8?
ionic
what is ionic bonding?
the electrostatic attraction between oppositely charged ions
what type of elements do ionic bonds form form?
metal and non-metal
what are the physical properties of ionic compounds?
- conducts electricity in molten/dissolved state
- high melting point
- soluble in polar solvents
why do ionic compounds only conduct electricity in molten state?
the ions are free to move and carry the electric current.
what is covalent bonding?
The electrostatic attraction between positive nuclei and a shared pair of bonding electrons.
what type of elements do covalent bonds form form?
non-metal
what factors do the polarity of a molecule depend on?
- presence of polar bonds
- geometry of molecule
what states are simple molecular compounds mostly in + why?
liquids and gases due to weak intermolecular forces
what is the electrical conductivity strength of simple molecular substances?
poor conductors of electricity
what are the physical properties of giant covalent structures?
- do not form discrete molecules
- do not conduct electricity
- insoluble
- high melting pt.
what are allotropes?
different forms of the same element in the same physical state
what are the allotropes of carbon?
- graphite
- diamond
- fullerene C60
- graphene
what is the structure of graphite?
- layers held together by weak intermolecular forces
- Each carbon atom is bonded to 3 other carbon atoms.
- Bond angle: 120
- Geometry: trigonal planar
what are the physical properties of graphite?
- layers can slide over one another
- good conductor of electricity
why is graphite a good conductor of electricity?
the delocalised electrons
that are free to move within the structure
what is the structure of diamond?
- Giant covalent structure
- Each carbon is bonded to 4 other carbon atoms
- bond angle: 109.5
- Geometry: tetrahedral
what is one physical property of diamond?
- does not conduct electricity
what is the structure and physical properties of fullerene?
- Each carbon atom is bonded to 3 other carbon atoms
- Structure consists of 12 pentagons and 20 hexagons.
- some electrical conductivity
what is the structure and physical properties of fullerene?
- Each carbon atom is bonded to 3 other carbon atoms.
- Bond angle between carbon atoms is 120
- Very good heat and electrical conductivity.
- Very thin (one layer thick) but also very strong.
what are london dispersion forces?
weak, temporary forces that arise due to the random movement of electrons
What are Dipole-Dipole Interactions?
attractions between polar molecules, where the positive end of one molecule is attracted to the negative end of another.
What is Hydrogen Bonding?
hydrogen covalently bonded to F, O, N
London dispersion forces increases with increasing ………. ………….
molar mass
what is metallic bonding?
the electrostatic attraction between a lattice of positive ions and delocalized electrons.
what does strength of metallic bonds depend on?
- charge of the ions
- radius of the metal ion
why are metals malleable?
the metallic bond remains intact even if the structure is distorted.
why are metals reflective?
the delocalized electrons in the metallic structure reflect
light
what is the relationship between the strength of metallic bond and ionic charge?
stronger ionic charge = stronger bond
what is the relationship between the strength of metallic bond and size of radius?
smaller radius = stronger bond
what are alloys?
materials that are composed of two or more metals or a metal and a non-metal.
why are alloys less malleable?
The added metal atoms can distort the lattice structure making it more difficult for the layers to slide over each other.
what is a sigma bond?
head-on overlap of s orbitals
