BLOCK 2 Bonding Flashcards
Define electronegativity
A measure, the measure of the ability an atom to attract a shared pair of electrons in a covalent bond
Why does electronegativity increase across a period?
Increase in:
- nuclear charge
- atomic radius
define a covalent bond
A shared pair of electrons within a bond
Where bond electrons have opposing spin
forces between molecules generally influence their
Physical properties
forces inside molecules generally influence their
chemical properties
order of bond strength
(from strongest to weakest)
-pure covalent
-ionic
-nonpolar covalent
-polar covalent
-hydrogen
-van der waals
Name the top four electronegative elements
-F
-O
-N
-Cl
name physical properties
-solubility
-conductivity
-m.p , b.p
-state at room temp
name chemical properties
-reactivity
what is intermolecular
forces between molecules
what is intramolecular
forces inside molecules
name intermolecular forces
-van der Waal’s
-dipole/dipole
-hydrogen bonds
name intramolecular forces
-ionic
-covalent
-metallic
name all covalent bonds
-pure
-nonpolar
-polar
-co-ordinate
what is a chemical bond?
an electrostatic force of attraction between atoms.
All electrostatic bonds refer to a +/- attraction
what is ionic bonding
an electrostatic attraction between oppositley charged ions
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 is a covalent bond formed
By sharing a pair of electrons (each electron donates an electron each to the shared pair)
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
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
more more more
more ELECTRONS
more VAN DER WAAL’S
more HEAT
what is a polar bond
a separation of charge due to unequal sharing of electrons
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)
