The electrons and the quantum mechanical model

Question 1

electromagnetic radiation

Answer 1

consists of energy particles that move as waves of energy

Question 2

planck’s constant

Answer 2

6.626 x 10^-34 m2 kg/s =Js

Question 3

equations for electromagnetic radiation

Answer 3

c= vλ

E= hv = hc/λ

h= planck’s constant

Question 4

electromagnetic spectrum

Answer 4

radiowaves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays

Question 5

atomic spectrum

Answer 5

when light from a heated element passes through a prism, it separates into distinct lines of color separated by dark areas. each element has its unique atomic spectrum of distinct lines

Question 6

what are the lines in an atomic spectrum are associated with

Answer 6

with the changes in the energies of the electrons

Question 7

quantum

Answer 7

very specific levels where the energy of the electron is limited to

Question 8

principal quantum number

Answer 8

energy levels

n=1, n=2, n=3

energy increases as the value of n increases and electrons are further away from the nucleus

distances decrease quadratically

Question 9

when do electrons move to a higher energy level

Answer 9

when they absorb energy

Question 10

how can you promote an electron to a higher energy level?

Answer 10

provide an amount of energy equal to the level difference

Question 11

what happens when an electron falls back to a lower energy level?

Answer 11

light is emitted

Question 12

what is the energy emitted or absorbed equal to

Answer 12

the difference between 2 energy levels

Question 13

why cannot Bohr’s model be correct?

Answer 13

1. electrons moving at a constant speed around the nucleus would emit energy and this does not happen
2. electrons would progressively slow down and fall on the nucleus and this does not happen

Question 14

particle-wave duality of subatomic particles

Answer 14

electrons can behave like a particle or a wave

Question 15

the electron has a wavelength equal to:

Answer 15

λ= h/mv

Question 16

uncertainty principle

Answer 16

we cannot know exactly the position and speed of an electron

Question 17

why do we want to know where the electron is around an atom?

Answer 17

if the electron is closer to the nucleus it is less prone to share with other elements and thus its position can influence the atom’s reactivity: electrons with the same levels of energy will form more stable bonds

Question 18

what does the wave function depend on?

Answer 18

on the number of electrons in the atom

Question 19

what is the value of the square of the wave function ψ^2?

Answer 19

the probability of finding an electron in a specific region in space

Question 20

what does the wave function depend on?

Answer 20

values of the wave function depend on 3 integer numbers: n,l,m

Question 21

orbitals

Answer 21

volumes in space where we have a defined probability of finding an electron

Question 22

energy of a hydrogen atom

Answer 22

E= -1/n^2 x 2.18 x 10^-18 J

Question 23

the 4 quantum numbers

Answer 23

1. principal quantum number
2. angular momentum quantum number
3. magnetic quantum number
4. electron spin number

Question 24

angular momentum quantum number

Answer 24

l
describes the shape of the regions where there is non-zero probability of finding an electron

eg. if n=3, l= 0,1,2

Question 25

magnetic quantum number

Answer 25

m
specifies the orientation in space of the orbital

if n=3, m=-2,-1,0,1,2

Question 26

electron spin number

Answer 26

s
+- 1/2

if an electron is placed in a mf its energy will be based on the direction it spins in

Question 27

how many orbitals in a level

Answer 27

n^2

Question 28

how many orbitals in a sublevel

Answer 28

2l + 1

Question 29

l=0, l=1, l=2, l=3

Answer 29

l=0 s
l=1 p
l=2 d
l=3 f

Question 30

what do wave functions contain

Answer 30

at least one node: the point where the wave function has a value of zero, and thus regions with a probability of finding the electron is zero

Question 31

what happens as we go further up in energy

Answer 31

we will have more nodes

nodes are proportional to n: number of nodes n-1

Question 32

level n=2

Answer 32

l can assume the value of 1, referred to as p orbital. m ca be equal to -1, 0, 1 so there are 3 p orbitals. A p orbital has 2 regions of high probability which gives a dumbshell shape

Question 33

wave function

Answer 33

describes the probability of finding a particle

Question 34

what does it mean if an orbital has a node?

Answer 34

it can have positive and negative phases: which important for chemical bonding

Question 35

Pauli exclusion principle

Answer 35

1. each orbital can hold a maximum of 2 electrons
2. electrons in the same orbital repel each other (coulomb’s law)
3. electrons in the same orbital must have their magnetic spins cancel

Question 36

madelung- kleckovskij rule

Answer 36

atomic orbitals are filled in order of increasing n+l

Question 37

why is E(s) < E(p) < E(d) < E(f)

Answer 37

1. shielding: when an electron is further away from the nucleus, it feels a nuclear charge that is partially shielded by the inner electrons. it experiences a charge Z(eff)<Z
2. penetration: when a higher level electron gets closer to the nucleus, it experiences a higher nuclear charge and its energy decreases

Question 38

chromium configuration

Answer 38

[Ar] 4s1 3d5

Question 39

copper configuration

Answer 39

[Ar] 4s1 3d10

Question 40

lewis symbols

Answer 40

represent the valence electrons as dots placed on sides of the symbol of an element

Question 41

describe how atomic size changes along a period and going down a group

Answer 41

atomic size increases going down a group but decreases going from left to right across a period

Question 42

what determines the atomic size

Answer 42

by the atom’s atomic radius, the distance between the nucleus and the outermost electron-accessible orbital.

Question 43

ionisation energy

Answer 43

the energy needed to remove one mole of the outermost electrons in the gaseous phase

Question 44

describe how ionisation energy changes

Answer 44

as the distance from the nucleus to the valence electrons increases, the ionisation energy decreases.
ionisation energy decreases down a group as the distance between the nucleus and valence electrons increases.
ionisation energy increases as we move along a period as the number of protons strengths the attraction of the nucleus for the valence electrons

Question 45

how can divalent cations be obtained?

Answer 45

from 2 subsequent ionisations

Question 45

how does the first ionization energy compare to the second ionization energy?

Answer 45

the first one if smaller than the second one

Question 46

electron affinity

Answer 46

the energy released by an element when it gains an electron

Question 47

describe whether electron affinity is endothermic or exothermic

Answer 47

1st EA: endothermic
2nd EA: exothermic

Question 48

describe how metallic character changes

Answer 48

as we go down a group metallic character increases because the valence electrons are easier to remove when they are further from the nucleus

as we go along a period metallic characteristics decrease as the number of protons increases which strengthens the attraction of the nucleus for the valence electrons and makes it more difficult to remove a valence electron.