Bonding Flashcards

Question

Examples of complex shapes - IF4+

Answer 1

I has 7 electrons in its outer shell. 4 F’s add 4 more electrons. Remove one electron as positively charged. This makes a total of 10 electrons made up of 4 bond pairs and 1 lone pair. The means it is a variation of the 5 bond pair shape (trigonal bipyramidal)

Answer 2

ability or tendency of an atom to attract a pair of electrons in a covalent bond. This depends on the number of protons in the nucleus, the distance between outer electrons and the nucleus and the degree of shielding.

Answer 3

Attraction exists between the positively charged protons in the nucleus and negatively charged electrons found in the energy levels of an atom. An increase in the number of protons leads to an increase in nuclear attraction for the electrons in the outer shells. Therefore, an increased nuclear charge results in an increased electronegativity.

Answer 4

The atomic radius is the distance between the nucleus and electrons in the outermost shell. Electrons closer to the nucleus are more strongly attracted towards its positive nucleus. Those electrons further away from the nucleus are less strongly attracted towards the nucleus. Therefore, an increased atomic radius results in a decreased electronegativity.

Answer 5

• Shielding - Filled energy levels can shield (mask) the effect of the nuclear charge causing the outer electrons to be less attracted to the nucleus. Therefore, the addition of extra shells and subshells in an atom will cause the outer electrons to experience less of the attractive force of the nucleus. Sodium (period 3, group 1) has higher electronegativity than caesium (period 6, group 1) as it has fewer shells and therefore the outer electrons experience less shielding than in caesium. Thus, an increased number of inner shells and subshells will result in a decreased electronegativity

Answer 6

when one atom has a greater tendency to attract electron pairs. This makes them polar covalent where partial charges that result from the uneven balance of electrons.

Answer 7

Eg: HF The electrons are closer to fluorine due to its high difference in electronegativity. This causes a greater electron density around fluorine due to the uneven distribution. This causes a slight negative charge around the fluorine and a slight positive around the hydrogen.

Answer 8

There is a decrease in electronegativity going down the group The nuclear charge increases as more protons are being added to the nucleus However, each element has an extra filled electron shell, which increases shielding The addition of the extra shells increases the distance between the nucleus and the outer electrons resulting in larger atomic radii Overall, there is decrease in attraction between the nucleus and outer bonding electrons

Answer 9

Electronegativity increases across a period The nuclear charge increases with the addition of protons to the nucleus Shielding remains relatively constant across the period as no new shells are being added to the atoms The nucleus has an increasingly strong attraction for the bonding pair of electrons of atoms across the period of the periodic table This results in smaller atomic radii

Answer 10

• Non-polar molecules have a 0 dipole moment, the more polar the molecule, the greater the dipole moment. • For some molecules, e.g HCI, the polar bond gives rise to a permanent dipole- there is a positive and negative end to the molecule. • However, the shape and symmetry of the molecule plays a role in determining whether the molecule is polar overall. • For a molecule to be polar overall, it must contain polar bonds and its not in the same place shape must be such that the centres of positive and negative charge are

Answer 11

• Van der Waal’s forces (london and dispersion forces) • Dipole-dipole forces (stronger than van der Waal’s) • Hydrogen bonding

Answer 12

• The electron charge cloud in non-polar molecules or atoms are constantly moving. During this movement, the electron charge cloud can be more on one side of the atom or molecule than the other • The electron movement gives rise to instantaneous dipole on the moment • This temporary dipole has an inductive effect on the electron clouds of neighbouring molecules, the partial negative end of one neighbouring molecule resulting in an induced charge.

Answer 13

• the strength of the forces increase with mass • As moles get bigger, there are more electrons so instantaneous dipole moments increases • with halogens atom get bigger, more forces because there are more electrons so there are greater forces ( not strong).

Answer 14

For small molecules with the same number of electrons, permanent dipoles are stronger than induced dipoles Butane and propanone have the same number of electrons Butane is a nonpolar molecule and will have induced dipole forces Propanone is a polar molecule and will have permanent dipole forces Therefore, more energy is required to break the intermolecular forces between propanone molecules than between butane molecules So, propanone has a higher boiling point than butane

Answer 15

Polar molecules have permanent dipoles The molecule will always have a negatively and positively charged end Forces between two molecules that have permanent dipoles are called permanent dipole - dipole forces The δ+ end of the dipole in one molecule and the δ- end of the dipole in a neighbouring molecule are attracted towards each other

Answer 16

Hydrogen bonding is the strongest form of intermolecular bonding Intermolecular bonds are bonds between molecules Hydrogen bonding is a type of permanent dipole – permanent dipole bonding

Answer 17

Hydrogen bonding is the strongest form of intermolecular bonding Intermolecular bonds are bonds between molecules Hydrogen bonding is a type of permanent dipole – permanent dipole bonding

Answer 18

When hydrogen is covalently bonded to an O, N or F, the bond becomes highly polarised The H becomes so δ+ charged that it can form a bond with the lone pair of an O, N or F atom in another molecule For example, in water Water can form two hydrogen bonds, because the O has two lone pairs

Answer 19

Hydrogen bonding in water, causes it to have anomalous properties such as high melting and boiling points, high surface tension and a higher density in the liquid than the solid

Answer 20

Water has high melting and boiling points due to the the strong intermolecular forces of hydrogen bonding between the molecules in both ice (solid H2O) and water (liquid H2O) A lot of energy is therefore required to separate the water molecules and melt or boil them

Answer 21

The enthalpy changes increase going from H2S to H2Te due to the increased number of electrons in the Group 16 elements This causes an increase in the instantaneous dipole - induced dipole forces as the molecules become larger H2O is an anomalous cos of hydrogen

Answer 22

Water has a high surface tension Surface tension is the ability of a liquid surface to resist any external forces The water molecules at the surface of liquid are bonded to other water molecules through hydrogen bonds These molecules pull downwards the surface molecules causing the surface of them to become compressed and more tightly together at the surface This increases water’s surface tension

Answer 23

the relatively long bond lengths of the hydrogen bonds means that the water molecules are slightly further apart than in the liquid form Therefore, ice has a lower density than liquid water by about 9%

Answer 24

A polar covalent bond forms when the elements in the bond have different electronegativities . (Of around 0.3 to 1.7) When a bond is a polar covalent bond it has an unequal distribution of electrons in the bond and produces a charge separation, (dipole) ends.

Answer 25

A symmetric molecule (all bonds identical and no lone pairs) will not be polar even if individual bonds within the molecular are polar The individual dipoles on the bonds ‘cancel out due to the symmetrical shape of the molecule. There is no net dipole moment: the molecule is non-polar

Answer 26

The more electrons there are in the molecule the higher the chance that temporary dipoles will form. This makes the Van der Waals stronger between the molecules and so boiling points will be greater.

Answer 27

These are also called induced dipole-dipole interactions. In any molecule the electrons are moving constantly and randomly. As this happens the electron density can fluctuate and parts of the molecule become more or less negative i.e. small temporary or transient dipoles form. These instantaneous dipoles can cause dipoles to form in neighbouring molecules. These are called induced dipoles. The induced dipole is always the opposite sign to the original one.

Answer 28

The increasing boiling points of the halogens down the group 7 series can be explained by the increasing number of electrons in the bigger molecules causing an increase in the size of the Van der Waals between the molecules. This is why I2 is a solid whereas Cl2 is a gas.

Answer 29

Long chain alkanes have a larger surface area of contact between molecules for Van der Waals to form than compared to spherical shaped branched alkanes and so have stronger Van der Waals.

Answer 30

•Permanent dipole-dipole forces occurs between polar molecules •It is stronger than Van der Waals and so the compounds have higher boiling points •Polar molecules have a permanent dipole. (commonly compounds with C-Cl, C-F, C-Br H-Cl, C=O bonds) •Polar molecules are asymmetrical and have a bond where there is a significant difference in electronegativity between the atoms.

Answer 31

It occurs in compounds that have a hydrogen atom attached to one of the three most electronegative atoms of nitrogen, oxygen and fluorine, which must have an available lone pair of electrons. e.g. a –O-H -N-H F- H bond. There is a large electronegativity difference between the H and the O,N,F

Answer 32

Hydrogen bonding is stronger than the other two types of intermolecular bonding.

Answer 33

The anomalously high boiling points are caused by hydrogen bonding between the molecules. The general increase in boiling point from H2S to H2Te is caused by increasing Van der Waals forces between molecules due to an increasing number of electrons.

Answer 34

The dipole moments cancel out because of the symmetry of the molecule

Answer 35

Bigger molecule more electrons more van der walls forces so cause a greater force

Answer 36

The attraction of the loan pay on the O and the partially positive charged H on the oh group of other molecules