1.4 Bonding Flashcards
what is ionic bonding
an electrostatic attraction between oppositley charged ions
what is an ionic crystal
-lattice of ions
-held together by electrostatic attraction of oppositely charged ions
Why do ionic compounds have high melting points
- strong electrostatic attraction between oppositely charged ions require lots of energy to break
- therefore they have high melting points
What is a covalent bond
- involves the sharing of electron pairs between atoms
- forms due to electrostatic attraction between the positive nuclei of the bonded atoms and the negative electrons which are between the two nuclei
What is ionic bonding found between
non-metal + metal
What is ionic bonding found between
non-metal + metal
What is covalent bonding found between
non metal + non-metal
What is metallic bonding found between
metal + metal
why are metals conductive?
due to the sea of delocalised electrons
what is the point of chemical bonding
chemical bonding occurs for atoms to get a stable electron configuration
define a chemical bond
a chemical bond is an electrostatic force of attraction between elements with a positive and negative charge
giant covalent
high melting point
simple covalent
low melting point (small molecules)
how to drawn ionic bonding
dot and cross diagram
how to draw covalent bonding
dot and cross diagram but with overlapping orbital
Why is a covalent bond formed
By sharing a pair of electrons (each electron donates an electron each to the shared pair)
What is bond polarity
separation of electric charge along a bond.
polar bonds occur when electrons in the bond are not shared equally
Electronegativity
The ability of an atom to attract the shared pair of electrons (electron density) in a covalent bond towards itself
Factors that affect Electronegativity
- nuclear charge
- atomic radius
- shielding
Electronegativity trend across a group:
- increases across a group
Electronegativity down a period
- Decreases down a period
What properties cause a dipole bond to form
The electronegativities of the elements are different
What bond occurs when there is no dipole?
pure covalent
what bond occurs when there is a dipole?
polar covalent
where will delta- go?
The more electronegative
where will delta+ go?
The least electronegative
What is a temporary dipole
an uneven distribution of electrons, making one half of the molecule more negatively charged than the other
What is a permanent dipole
- when 2 covalently bonded atoms have different electronegativities, forming a polar bond. This causes a delta- and delta+ region
What is an induced dipole
created when electron distribution around a molecule is influenced by a charged particle
Compare the bond character in a covalent bond and ionic bond
covalent bond - electrons equally shared between atoms, no overall charge
ionic bond - complete transfer of electrons between atoms to produce ions will full charges
what type of intermolecular forces are there
- Temporary dipole
- Permanent dipole
- Hydrogen bonding
what is a dipole
A molecule with 2 different charges
hydrogen bonding
permanent dipole-dipole but occurs when a H is bonded to:
- fluorine
- oxygen
- nitrogen
Strength of intermolecular forces:
h-bonding > permanent dipole-dipole > van der Waals’
this means that H-bonding has a higher boiling point.
what is a lone pair of electrons
a pair of electrons in a valence shell that are no involved in bonding
What happens to boiling points across a group
they increase
why do boiling point increase across a group
- number of electron increase
- strength of intermolecular forces increase (more electrons = greater strength)
why are boiling points of Group 4 hydrides lower than hydrides of Groups 5, 6 and 7
5, 6 and 7 are more likely to have dipole-dipole
