Thermochemistry and Properties

Question 1

Electronegativity explanation

Answer 1

• electronegativity is the ability of an atom to attract a bonding pair of electrons within a covalent bond.

decrease
eg: — the bonding electrons in energy level is further away from the nucleus and thus is less strongly attracted to the nucleus, the electron in the outermost shell of – atoms will have increased shielding from inner shell electrons, this inner-shell will cause electron repulsion, causing bonding pair of electrons to be further away from the attraction of the nucleus, thus it is more electronegative

increase
• Across a period: the electronegativity increases as the nuclear charge increases (more protons) and electrons are added in the same energy level (thus shielding is constant). Overall, the greater effective nuclear charge experienced by bonding electrons pulls them more strongly, increasing the electronegativity value.

Question 2

Atomic Radii Explanation Increase

Answer 2

It will increase when the atomic radius goes down a group
- Increasing electron shell - further away
- inner electron shields outer electrons - reduce the electrostatic attraction.

Eg; This is due — atom is larger than – atom because there is an increase in electron shells which will go into a new energy level that is further away from the positively charged nucleus, inner electrons will shield the outer electron shell causing a weak electrostatic attraction between nucleus and valance electrons.

Question 3

Atomic Radii Explanation Decrease

Answer 3

It will decrease when the atomic radius goes across a group
- greater nuclear charge - stronger attraction with electrons

Eg; -Both — atom have the same number of electron shells and energy level but — has a larger amount of proton/nuclear charge thus have a stronger attraction for valance electron, pulling them in closer resulting in a smaller radius.

Question 4

Ionic radius Explanations

Answer 4

+/Na+) cations are smaller than parent atoms
an whole outer atom shell is lost reduced distance between nucleus and outermost electrons. but they both have the same nuclear charge thus electrostatic attraction on electron cloud in the cation is greater than neutral atom, resulting in a small cation size.

-/Cl-) anions are bigger than the parent atoms
The electron-electron repulsion experienced by the electron cloud of the anion (cl-) will be greater than the neutral atom due to more electron gain electron more repulsion in shell. they both have the same amount of nuclear charge but electrostatic attraction on electron cloud for anion is less than the neutral atom resulting in a larger anion size.

Question 5

Ionisation Explanation Increase

Answer 5

Ionisation is the minimum energy that is needed to remove 1 mole of an electron from each atom in 1 mole of a gaseous atom.

Ionisation energy increase from left to right - moving across period. This will cause an increase in nuclear charge due to increasing electron shells and attraction force for the nucleus and valance electron as they move along. As electron added in same energy level increase across period, there is no repulsion between energy levels. The nuclei with a greater number of protons have a stronger electrostatic attraction for the valence electrons in the — shell, thus the energy to
remove an electron is greater.

Ionisation decrease when moving downwards as there is a increase in election shells/energy levels making electron move further away from the nucleus producing a shielding effect where inner shells election shield outer electrons from attractive forces of the nucleus. thus the largest atom with lots of electron shell have valance electron that are weakly attracted to the nucleus and is easier to remove - less energy required

Question 6

Temperoary dipoles, permant, hydrogen,

Answer 6

temporary dipole are the weakest attractive force, Permanent dipoles are a stronger attractive force
hydrogen bonding is strongest
all of them are
weak intermolecular forces)

and ionic and covalent stronger than them.

Question 7

Enthaply of fusion and why is vap greater than fus
fush solid to liquid
vap - liq to gas
sub solid to gas

Answer 7

Enthalpy of fusion is the energy required to change 1 mol of a substance\
(NH3) from a solid to a liquid.

Fusion of NH3 only requires sufficient heat energy to break/overcome some of the ionic bonds, whereas vaporisation requires much more heat
energy to overcome all the ionic bonds, therefore the vap is larger than fus

Question 8

Non polar and polar in water

Answer 8

NH3, n is attracted to the H, and H is attracted to the O
thus Nh3 and h20 has strong attraction, allowing Nh3 to disrput and go between water molecules

Non polar - they have weak intermolecular forces between nonpolar and water and they cannot disrupt and go in between water molecules as they have more stronger attractions between themselves.

Question 9

Ionic substance in water

Answer 9

they both strongly attract to each and pull out its lattice.

Question 10

anion ionic radius

Answer 10

• electron repulsion as anion has more elctron thus more repulsion in shell
• electrostatic attraction on electron cloud for anion is less than neutral atom thus anion has larger size

Question 11

Temp dipoles

Answer 11

depends on molar mass strength and increase surface area between molecules will create stronger temp dipoles

Question 12

cation radius

Answer 12

whole outer shell is lost reducing distance between nucleus and outer electrons and electrostatic attraction on electron cloud for cation is larger than the neutral atom thus cation is smaller size.