AS Chemistry help - atomic structure

Hi, stuck with a few questions, thanks for all help in previous threads.

1. State and explain the general trend in first ionisation energies across a period of s-block and p-block elements. (3 marks).

2 (a). Place the following orbitals in ascending order of energy, starting with a 1s orbital. (3 marks)
1s, 3p, 5d, 4s, 4f, 6p, 5s, 2p, 3d.

(b) Explain why the first row of d-block elements is placed in the fourth row of the Periodic Table, when, generally, their electronic configurations change by the addition of electrons to the third shell. (2 marks)

Thanks!

Reply 1

frank_drebin

16

Hi

1) The general trend is for the first ionisation enthalpy to increase across a period. It increases because, the nuclear charge increases on going across the Period. This means that the electrostatic force of attraction between the nucleus and the electron is greater. Therefore more energy is needed to remove it

2) 1s, 2p, 4s, 3d, 4f, 5s, 5d, 6p. The important point is that the 4s subshell fills before the 3d subshell as it has a lower energy level

3) I think this question is related to the 4s subshell. Although their electron configurations change by the addition of electrons to the third shell, or the 3d subshell which is usually partially filled, it is the 4s subshell that fills first. Therefore they are placed into the fourth row. I think the important point is to realise that the rows go with the primary energy levels

Reply 2

arsenalfan.

OP

1

frank_drebin

Hi

1) The general trend is for the first ionisation enthalpy to increase across a period. It increases because, the nuclear charge increases on going across the Period. This means that the electrostatic force of attraction between the nucleus and the electron is greater. Therefore more energy is needed to remove it

2) 1s, 2p, 4s, 3d, 4f, 5s, 5d, 6p. The important point is that the 4s subshell fills before the 3d subshell as it has a lower energy level

3) I think this question is related to the 4s subshell. Although their electron configurations change by the addition of electrons to the third shell, or the 3d subshell which is usually partially filled, it is the 4s subshell that fills first. Therefore they are placed into the fourth row. I think the important point is to realise that the rows go with the primary energy levels

Thanks for your reply, I really apprecaite your help. :smile:

Could you explain (not answer) to me question 2 in more detail? What does it mean by ascending order of energy, and how would I know the energy for each orbitals?

Could you explain to me what question 3 is asking, and what it means by "primary energy levels", and "first row of d-block elements ".

Thanks!

Thanks!

Reply 3

frank_drebin

16

Well for question 2, I think what it means is, if electrons were being filled into these separate subshells which would they fill first? When electrons fill subshells they always fill those which have the lowest energy level first, then the next lowest, etc

For question 3, I think the question is asking that as most of the chemical reactions involved with the d- block elements take place in the 3rd shell (which includes the 3d subshell), why are they not included in the 3rd row, but rather the 4th? They are included in the fourth row as the fourth shell fills first(the 4s subshell as it has a lower energy than the 3d subshell)- this is what I meant when I wrote primary energy level.
The first row of the d-block elements are Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn

Reply 4

arsenalfan.

OP

1

Thanks for your reply, I apprecaite it!

(a) Could you explain to me how you knew and found out which subshell has the lowest energy level first, and then the next lowest etc..?
(b) What do you mean by d-block elements? are thye elements ending with a d subshell?

BTW Could you help me with these 2 questions? Thanks!

1. Explain the statement "Between groups 2 and 3, and between groups 5 and 6, this overall trend (regarding to question 1 in my first post, which in this case if referring to first ionisation energies), is contravened. (6 marks)

Draw electron in box notations for beryllium, boron. And Nitrogen and Oxygen, and then explain the statement above.

Can you please help me with the statement bit, thanks alot! the drew out the electron in box notations already. :smile:

-------------------------
With the aid of labelled diagrams, describe the 3 dmensional shape of the following atomic orbitals:

(a) an s atomic orital (2 marks)
Description -
Diagram-

(b) a p[y], atomic orbital. (2 marks)
Description -
Diagram-

Thanks alot for all your help, I really apprecaite it! :smile:

Reply 5

giggsy

D block elements mean the outer electron occupies the d orbital.

electron boxes are just like arrow up and arrow down

Reply 6

frank_drebin

16

For 1, the ionisation enthalpy decreases because as you go down the groups, the elements become more reactive. Theefore the electrons are more easily lost and less energy is needed

For the diagrams, sorry I really dont know what to draw :frown:

I found the following site-
- http://winter.group.shef.ac.uk/orbitron/AOs/2s/index.html

Reply 7

arsenalfan.

OP

1

Thanks for your replies, could you check my previous post, I edited the top part which has a few questions!

Thanks again!

p.s. does ionisation enthaply = ionisation energy?

(a) Could you explain to me how you knew and found out which subshell has the lowest energy level first, and then the next lowest etc..?

Reply 8

frank_drebin

16

The first shell, n=1 has only one sub- shell (s)
The second shell, n=2 has two sub- shells (s and p)
The third shell, n=3 has three sub- shells (s, p and d)
The fourth shell, n=4 has four sub- shells (s, p, d and f)

s sub- shell can hold a maximum of 2 electrons
p sub- shell can hold a maximum of 6 electrons
d sub- shell can hold a maximum of 10 electrons
dont know about f sub- shell, sorry

So, there is a basic rule which decides which sub- shell has the lowest energy level, the next sub- shell which then has the lowest, etc.
The 1s subshell always fills first. Now you have to decide which sub- shell will fill next. In order to decide this, you have to look firstly at the number in front of the sub- shell, the prinicpal quantum number- when this increases the energy level of the sub- shell also increases. So, 3s sub- shell has greater energy than the 2s sub- shell.
You then have to look the kind of the sub- shell. The s sub- shell always fills first, then the p, then the d, etc.
So for an element like sodium, atomic mass=11, its electron configuration would be-
- 1s2 2s2 2p6 3s1