atomic orbitals and electron configuration

Question 1

define electron configuration

Answer 1

the arrangement of electrons in an atom

Question 2

in the current accepted model of the atom, what do electrons have?

Answer 2

fixed energies, therefore they move around the nucleus in certain regions of the atom called shells/energy levels

Question 3

define the term ‘principal quantum number’

Answer 3

the principal quantum number is also known as n, and is used to number the energy level or quantum shell

Question 4

relationship between principal quantum number and nucleus

Answer 4

lower principal quantum number the closer it is to the nucleus
the first shell is closest to the nucleus hence n=1

the higher the principal quantum number the greater the energy of the shell and the further it is from the nucleus

Question 5

what is the maximum number of electrons each energy level can hold?

Answer 5

2n2

Question 6

therefore, what is the fixed number of electrons held in each energy level?

Answer 6

n = 1 means 2 electrons
n = 2 means 8 electrons
n = 3 means 18 electrons
n = 4 means 32 electrons

Question 7

what are these energy levels divided into?

Answer 7

sub levels

Question 8

state the four main sublevels found within an atom

Answer 8

s, p, d, f
elements with more than 57 electrons have an f sublevel

Question 9

what is an electron now considered to be?

Answer 9

a cloud of negative charge

Question 10

what is an atomic orbital?

Answer 10

the probability of finding an electron in a given volume of space (probability 95% therefore). the shapes of the molecules are influenced

Question 11

what is the maximum number of electrons each orbital can hold?

Answer 11

2

Question 12

how many orbitals does each sublevel have and electrons as a result of this?

Answer 12

s : one orbital (1 x 2 = total of 2 electrons)
p : three orbitals (3 x 2 = total of 6 electrons)
d : five orbitals (5 x 2 = total of 10 electrons)
f : seven orbitals (7 x 2 = total of 14 electrons)

Question 13

what orbitals do each energy level have?

Answer 13

1st - 1 s orbital
2nd - 1 s, 3 p
3rd - 1 s , 3 p , 5 d

order:
1s
2s 2p
3s 3p 4s
3d 4p 4d
5s 5p 5d

Question 14

describe the shape of an s orbital

Answer 14

spherical
the size of an s orbital increases with increasing shell number

Question 15

describe the shape of a p orbital

Answer 15

dumbbell shape
every shell has three p orbitals except for the first one (n = 1)
The lobes of the p orbitals become larger and longer with increasing shell number
therefore

Question 16

describe ‘spin’, a property electrons have0

Answer 16

• two electrons in the same orbital must have opposite spins
  the electrons are represented by the arrows pointing up and down depending on the direction of the spinning

Electrons are only paired when there are no more empty orbitals available within a subshell, in which case the spins are the opposite spins to minimize repulsion

Question 17

ground state

Answer 17

The ground state is the most stable electronic configuration of an atom which has the lowest amount of energy

Question 18

the periodic table has different blocks of elements due to electron configuration. state what they are and the reason for this placement

Answer 18

s block elements have their valence (outer) electrons in a s orbital
p block elements have their valence (outer) electrons in a p orbital
d block elements have their valence (outer) electrons in a d orbital
f block elements have their valence (outer) electrons in a f orbital

Question 19

state the increase in energy for the sublevels

Answer 19

s < p < d < f
3d orbital differs from this role as it is higher in energy compared to the 4s sublevel

Question 20

what are all orbitals in the same subshell said to be?

Answer 20

degenerate (same energy)

Question 21

what are the rules for allocating electrons to atomic orbitals?

Answer 21

atomic orbitals of the lowest energy are filled first - lowest energy level with lowest sublevel therefore.
atomic orbitals of the same energy fill singly before pairing starts. this is because electrons repel each other.
no atomic orbital can hold more than two electrons.

Question 22

explain the order when writing electron configuration

Answer 22

e.g. 1s1
principal quantum number - subshell - number of electrons

Question 23

what does writing out electron configuration tell us?

Answer 23

how the electrons in an atom or ion are arranged in their shells, subshells and orbitals

Question 24

what does full electron configuration describe?

Answer 24

the arrangement of all electrons from the 1s subshell up
e.g. calcium - 1s2 2s2 2p6 3s2 3p6 4s2

Question 25

what does the shorthand electron configuration describe?

Answer 25

using the symbol of the nearest preceding noble gas to account for however many electrons are in that noble gas
e.g. calcium - nearest noble gas is argon so [Ar] 4s2

Question 26

how are negative ions formed>

Answer 26

adding electrons to the outer subshell

Question 27

how are positive ions formed?

Answer 27

subtracting electrons from the outer subshell

Question 28

how do transition metals work in terms of electron configuration?

Answer 28

they fill the 4s subshell before the 3d subshell but lose electrons from the 4s first as it is lower in energy.

Question 29

give the electron configuration of potassium + in shorthand

Answer 29

1s2 2s2 2p6 3s2 3p6 4s1
[Ar] 4s1

Question 30

give the electron configuration of chromium + calcium

Answer 30

1s2 2s2 2p6 3s2 3p6 3d5 4s1 (chromium)
1s2 2s2 2p6 3s2 3p6 3d10 4s1 (copper)

Question 31

why are the electron configurations of chromium and calcium different to what would be anticipated?

Answer 31

chromium is not 3d4 4s2, copper is not 3d9 4s2 because its less energetically stable