c1 - atomic structure

charge and mass of e^-

charge: -1, mass: 1/1840

charge and mass of p

charge: +1, mass: 1

charge and mass of n

charge: 0, mass: 1

3 rules to follow when drawing angle of deflection

1. deflection only starts when the beam enters the electric field

2. deflection of beams of e^- and p occurs within the electric field in a parabolic path

3. beam continues on a straight line after leaving electric field

angle of defelction depends on?

charge or particle, q: greater = greater extent of deflection (D.P.)

mass of particle, m: greater = smaller extent of deflection (D.P.)

angle of deflection < angle of deflection and why

angle of deflection α < angle of deflection γ because mass of p (1) > mass of e^- (1/1840)

formula for angle of deflection

angle of deflection ∝ | charge / mass |

isotopic

atoms/ions, same no. of p

isotonic

atoms/ions, same no, of n

isoelectronic

atoms/ions/molecules, same no. of e^-

PQN/PQS, n : larger n means? (3)

1. further the shell is from nucleus

2. increase in energy level of e^- in the shell

3. less tightly e^- attracted to nucleus

across the period, no. of PQN/PQS

same

down the group, no. of PQN/PQS

increases

PQN/PQS : subshells (SS) : type

1 : 1 : s

2 : 2 : s, p

3 : 3 : s, p, d

4 : 4 : s, p, d, f

each SS is made up of

degenerate orbitals (same energy, different oreintation)

define orbital

region/space in which there’s a increased probability of finding an e^-

each orbital can accomodate a max of how many SS

2

SS : orbital : max. no. of e^-’s

s : 1 : 2

p : 2 : 6

d : 3 : 10

3 properties of s orbital

1. shape: spherical (3D)

2. non directional: e^- density isn’t concentrated in any direction - probability of finding an e^- at a distance r, from nucleus is the same in all directions

3. size: size of orbital increases as (PQN/PQS) n increases (radius increases)

4 properties of p subshell

1. shape: dumbbell shaped

2. directional: e^- density is concentrated along x, y & z axes

3. size: size of orbital increases as (PQN/PQS) n increases

4. 3 p orbitals (p_x, p_y, p_z) in the same subshell have same size & shape just different oreintations

within each PQN/PQS, energies of subshells are

s < p < d < f

within each SS (of same PQN/PQS), orbitals are

degenerate (same energy, different oreintation)

why are energies of 3d and 4s subshells very close

1. when empty, 4s orbitals has loweer energy than 3d

2. when filled, 3d e^- will repel 4s e^- further from nuclues and up to a higher energy level

3. hence, 4s will have a higher energy level than 3d when filled = 4s will be more unstable/less stable (easier to lose) than 3d

4. resulting in 4s e^- being removed first before 3d e^- in the formation of positive ions

e^- with higher energy (futher away from nucleus) are

more unstable / less stable (more easily lose)

spdf notation: qufbau1S¹

1 = PQN, S = type of subshell, ¹ = no. of e^-

qufbau (building up) principle

e^- fill orbitals of lowest energy first before moving on to an orbital of next higher energy

hund’s rule

occupy orbitals singly first in parallel (same) direction

pauli exclusion rule

in a orbital, max no of e^- = 2 and they should spin the opp direction when in a orbital

4s fills up before 3d orbital but

write is as per normal (3d4s)

steps to write EC of ions

1. write EC of atom first

2. add/remove e^- from valence sub shell

sum of subscript =

no. of electrons in atom/ion

when e^- enters PQS/PQN,

new period starts

find period no. by looking at

PQN, n of e^- in the valence shell

find group no. by looking at

no. of valence e^-

atomic radius

distance between outermost e^- and the nucleus

factors affecting radius: nuclear charge

as no. of p increases/nuclear charge increases (outermost e^- are pulled nearer to nucleus)

• nuclear attraction on outermost e^- increases

• atomic radius decreases

factors affecting radius: sheilding effect by inner shell e^-

as more quantum shells are filled, sheilding effect by more inner shell e^- increases

• nuclear attraction on outermost e^- decreases

• atomic radius increases

factors affecting radius: no.of PQS

as no. of PQS increases, the outermost e^- are further from nucleus

• nuclear attraction on outermost e^- decrease

• atomic radius increases

trends in radius across the period: atomic

• no. of p/nuclear charge increases

• shielding effect (by innershell e^-) remains relatively constant

• greater nucler attraction on outermost e^-

• atomic radius across period decreases

trends in radius across the period: ionic

1. cation radii is smaller than its corresponding atom

2. anion radii is greater than its corresponding atom

3. ionic radii of each isoelectronic series decreases across period

why is cation radii is smaller than its corresponding atom

after the removal of outermost e^-, the cation has one less quantum shell of e^- and less shieding effect.

hence the nuclear attraction on the outermost e^- of cation is greater and the radius of cation is smaller than its corresponding atom.

why is anion radii is greater than its corresponding atom

when e^- are added to the same outermost shell, theres an increase in electron-electron repulsion. hence, resulting in an increase in the radius of anion compared to its corresponding atom.

why does ionic radii of each isoelectronic series decreases across period

across each isoelectronic series with the same EC, the nuclear charge increases while the shielding effect (by inner shell e^-) remains relatively constant. hence greater nuclear attraction on the outermost/valence e^-

trend of atomic radius down the group

down the group:

• increase in the no. of PQS

• valence e^- are further away from nuclues

• increase in shielding effect by inner shell e^- outweighs the increase in nuclear charge (or increase in protons)

• hence decreased attraction between nucleus and valence e^- / decreased nuclear attractions

• therefore, atomic radii decreases down the group

1^st ionisation energy of an element

energy required to remove one mole of e^- from one mole of GASEOUS atoms, M, to form one mole of GASEOUS cation, M⁺

2^nd ionisation energy

energy required to remove one mole of e^- from one mole of GASEOUS ions, M⁺ ions, to form one mole of GASEOUS cations, M²⁺

factors affecting IE

1. nuclear charge

2. shielding effect by inner shell e^-

3. no. of PQS

how does nuclear charge affect IE

as no. of p increase/nuclear charge increases:

• nuclear attraction on the e^- to be removed increases

• more energy is requried to remove valence e^-

• IE increases

how does shielding effect by inner shell e^- affect IE

as shielding effect by more inner shell e^- increases:

• nuclear attraction on the e^- to be removed decreases

• less energy is required to remove valenece e^-

• IE decreases

how does no. of PQS affect IE

as the no. of PQS increases, the e^- to be removed is further from the nucleus:

• nuclear attraction on the e^-to be removed decreases

• less energy required to remove valence e^-

• IE decreases

trends of 1^st IE: across the period

across the period, theres a increase in no. of p/nuclear charge while the shielding effect (by inner shell e^-) remains relatively constant. hence, greater nuclear attraction on the valence e^- . therefore, more energy is required to remove an valence e^- → 1^st IE increases across the period

2 anomalies of 1^st IE (small dips) across the period

1. ns² vs ns²np¹ configuration

2. np³ vs np⁴ configuration

anomalies of 1^st IE across the period: ns² vs ns²np¹ configuration (e.g. B and Be)

the 2p e^- of B is further away from the nucleus and hence, has a higher energy than the 2s e^- of Be. less energy is required to remove the 2p e^- of B. hence, less energy is required to remove the 2p e^- of B.

1^st IE of B is lower than that of Be (but still higher than that of Li)