Unit 1 Structure And Bonding Flashcards
What are the two main categories of bonding?
Intramolecular
The bonding that occurs between atoms
Intermolecular
The bonding that occurs between molecules
What are the 3 types of intramolecular bonds?
Pure covalent(non polar)
Polar covelent
Ionic
What are covalent bonds?
Are shared pair of electrons electrostatically attracted to both positive nucli
What are pure(non polar) covalent bonds?
Diatomic elements
Exist between atoms of same electronegativity, these electrons are shared evenly and the molecule has no ionic character
How do polar covalent bonds form?
When 2 atoms share a pair of electrons unequally
They have difference in electronegativity
What happens in a polar covalent bond, what is created?
The atom with the highest electronegativity becomes partially negative(symbol)
The atom with the lowest electronegativity becomes partially positive(symbol)
Dipole
What are polar covalent bonds known as?
Dipoles
When do ionic bonds form?
When electrons are transferred from one atom to another resulting in formation of ions
Large difference in electronegativity
What happens to atoms and how is bond held in ionic?
The atom with lowest electronegativity forms a positive ion
The atom with highest electronegativity forms negative ion
The bond is formed due to the electrostatic attraction between the positive and negative ions
What are ionic bonds between?
Non metal + metal
What happens to metal and non metal atoms?
Metal atoms forms positive ions when they lose electrons as they have lower electronegatives
Non metal forms negative ions when they gain electrons as they have higher electronegatives
What is bonding continuum?
Purecovalent->Polarcovalent->ionic
Pure covalent bonding and ionic bonding can be considered as being opposite ends of the bonding continuum
What are the cut off for difference in electronegatives for non polar,polar and ionic?
<0.5 non polar
0.5-1.8 polar
>1.8 ionic
What are the types of intermolecular bonds, what are they known as?
Van der waals forces
London dispersion forces
Pd-pd
Hydrogen bonding
What is the weakest intermolecular forces and how do they arise?
They exist between all atoms and molecules
Formed as a result of electrostatic attraction between temporary dipoles and induced dipoles caused by movement of electrons in atoms/molecules
What affects the strength of LDF forces?
The size of the molecule
Larger atoms and molecules have more electrons. This leads to larger dipoles being established
What are pd-pd intercations?
Molecules w permanent dipoles are polar(contains polar bonds)
Interrcation occurs when a partially negative charge in one molecule is attracted to partially positive charge of another
Why is water polar but carbon tetrachloride is non polar despite both containing polar bonds?
A substance that contains polar covenant bonds may not be overall due to symmetry
Water is angular=polar
Crabon… is tetrahedral so charges are symmetrical=non polar
What is the strongest intermolecular bond
Hydrogen bonding
What is needed for hydrogen bonding to occur?
When H atom is covalently bonded to a highly electronegative element(nitrogen,oxygen,fluorine)
What happens to hydrogen when it is bonded?
H becomes partially positive, atoms becomes partially negative
Positive h is electrosaticalky attracted to partial negative atom in another molecule
What happens to atoms of different intermolecular bonding for mp/bp?
The stronger intermolecular bonds(h bonding) more negery required to break bond and increased mo/bp
