Karteikarten
Chapter 6- Intermolecular forces and electronegativity
Karten in diesem Stapel (32)
- 1define electronegativityan atoms ability to attract the electron pair in a covalent bond
- 2what scale is used to measure electronegativitythe Pauling Scale
- 3what happens to electronegativity from H to F?it increases
- 4what is the trend for electronegativity across periods? (ignoring noble gases)increasing electronegativity
- 5what is the trend for electronegativity down groups? (ignoring noble gases)decreasing electronegativity
- 6what causes a covalent bond to become polar?when the two atoms that share the covalent bond have different electronegativities, so the bonding electrons are pulled towards the more electronegative atom
- 7in the polar bond, what is caused by the difference in electronegativitya permanent dipole forms
- 8what is a permanent dipole?a difference in charge caused by shift in electron density in the bond. the greater difference = more polar bond
-delta positive and delta negative charges form - 9are the covalent bonds in diatomic gases such as H2 and Cl2 polar or non polar and why?non-polar because the atoms have equal electronegativities and so electrons are attracted to both nuclei equally
- 10what factor is determines if a polar bond forms a permanent dipole or not?the arrangement of the polar bonds in the molecule
- 11Co2 is polar but explain if it has a permanentdipole or not and why?has 2 polar bonds but no overall dipole because polar bonds are arranged symetrically so dipoles cancel each other out. so CO2 is polar overall
- 12H2O has polar bonds but does it have a permanent dipole and why?Yes, permanent dipole because the polar bonds arranged unevenly so don't cancel each other out, charge positioned more towards oxygen atom
- 13when is a molecule 'purely covalent' and why?when the covalent bond is between atoms of a single element (e.g O2) as its only then that the electronegativity difference=0 so electrons are arranged completely evenly within the bond.
- 14are there many molecules that are 'purely ionic'no, most are somewhere between ionic and covalent
- 15how can electronegativity be used to predict what kind of bonding will occur?the more electronegative, the more ionic in character the bonding becomes
- 16what are intermolecular forces and are they strong or weak compared to ionic, covalent and metallic bonds.weak bonds between molecules, much weaker
- 17what are the 3 types of intermolecular forces?-induced dipole-dipole (london or dispersion) forces
-Permanent dipole-dipole interactions
-Hydrogen bonding = strongest - 18which molecules are induced dipole-dipole interactions (london forces) found between?all atoms and molecules
- 19why are induced dipole-dipole interactions (london forces) found between all atoms even noble gases?-electrons in charge clouds always moving fast
-at any particular time, electrons in atom likely to be more on 1 side vs other
-at this time atom has a temporary dipole
-this dipole can cause another temporary induced dipole in opposite direction on neighbouring atom
-2 dipoles attracted to each other
-2nd dipole causes dipole in 3rd atom
-electrons constantly moving so dipoles created and destroyed, but overall effect= atoms attracted to each other - 20which molecules have larger induced dipole-dipole forces?larger molecules and molecules with greater surface areas
- 21why do larger molecules/larger SA molecules have stronger induced dipole-dipole interactions?-larger molecules have larger electron clouds
-molecules with greater SA have more exposed electron clouds - 22explain a physical property thats affected by having larger induced dipole-dipole forcesliquids with stronger induced dipole-dipole forces have higher bpts, as more energy needed to overcome stronger intermolecular forces
- 23what happens to dipole dipole forces (and bpt) as you go down a group?increases, as number of shells of electrons increases so atomic/molecular size increases
- 24explain an example of where induced dipole-dipole forces hold molecules in a latticein iodine although covalent bonds hold iodine atoms in pairs to form molecules of I2, the molecules held in molecular lattice by induced dipole-dipole forces.
- 25which molecules form permanent dipole dipole interactions?polar molecules
- 26why do polar molecules form permanent dipole-dipole interactions?δ+ and δ- charges on polar molecules cause weak electrostatic forces of attraction between molecules
- 27which molecules does hydrogen bonding occur betweenONLY hydrogen with fluorine, nitrogen or oxygen
- 28explain hydrogen bondingHydrogen has high charge density as its so small and F,O,N very electronegative
-bond is polarised that a weak bond forms between the hydrogen of one molecule and lone paair on F,O,N in another molecule - 29explain how the hydrogen bonding in waterlone pairs on oxygen give delta negative charge which attracts delta positive on H
- 30explain how the Hydrogen bonding in effects properties-soluble in water
-higher bpts freezingpts
-ice less dense than water - 31explain how intermolecular forces explain trends in boiling pts-main factor= strength of induced dipole-dipole interactions (unless H bonds)
-explains why bpts Group 7 hydrides increase down group, although permanent dipole dipole interactions decreasing, number of electrons increases so strength of induced dipole-dipole interactions increases.
-but if 2 electrons similar n.o electrons, strength of induced dipole-dipole interactions similar, but if one more polar, have stronger permanent dipole-dipole interactions so higher bpt - 32how do intermolecular forces explain behaviour of simple covalent compounds?-low mpts/bpts as intermolecular forces between molecules weak so little energy to break, often liquid/gas rtp
-polar molecules water soluble, as can form H bonds with water (induced d-d insoluble)
-dont conduct electricity, as overall uncharged
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- Beschreibung
- A level Chemistry (Module 2 Foundations in Chemistry) Karteikarten am Chapter 6- Intermolecular forces and electronegativity, erstellt von Mehak Zahrah Faheem am 07/12/2018.
- Erstellt von
- Mehak Zahrah Faheem
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