M2, S2 Electronic structure

Question 1

What are the key characteristics of electron shells?

Answer 1

• electron shells: energy levels ÷ed into sub-shells ÷ed to orbitals
• Different energy levels have diff. no.s of sub-shells, each which with a diff. energy.
• shells are each given principal quantum numbers
• orbitals hold max. 2 electrons

Question 2

How does the distance from the nucleus affect the energy of a shell?

Answer 2

Shells further from the nucleus have a higher energy (and a larger principle quantum number) than shells closer to the nucleus.

Question 3

What are the names of the sub-shells?

Answer 3

s-, p-, d- and f- sub shells

Question 4

How can you calculate the maximum number of electrons that fit into each type of sub-shell?

Answer 4

Multiply the sub. shell’s number of orbitals by the maximum number of electrons in each orbital (2).

Question 5

How many orbitals do the s, p, d and f sub-shells have?

Answer 5

s: 1
p: 3
d: 5
f: 7

Question 6

How do you calculate the number of electrons in a given energy level?

Answer 6

• Find each type of sub-shell in the shell
• Put the number of the shell it’s in front of each. (This tells you how many of each sub-shell there are).
• Find the total number of electrons using:

no. of electrons in a sub-shell =

number of orbitals (1 (for s), 3 (for p) 5 (for d) or 7 (for f)) x max. no. of electrons in each orbital (2)

• Add the number of electrons of each type of sub-shell together, to get the total number of electrons in the shell (the energy level).

Question 7

What pattern can you see as you go from the first to the fourth sub-shell.

Answer 7

• From the first to the fourth sub-shell the new sub-shells appear in this order:

s, p, d, f

• The number before each sub-shell just tells you how many of each type there are.
• The number of each type of sub-shell (e.g. 2s or 3p) matches the number of the shell it’s in (1st, 2nd, 3rd or 4th).
• As you move to the next shell a new sub-shell appears. How many there are of this type of sub-shell will match the number of the shell it’s in.

Question 8

Given that the s, p, d and f shells have 1, 3, 5 and 7 orbitals respectively, list the sub shells and calculate the the maximum number of electrons that fit in each type of sub-shell.

Answer 8

Multiply the number of orbitals by the maximum number of electrons in each orbital (2).

Question 9

Find the number of electrons in the 1st, 2nd, 3rd and 4th energy levels

Answer 9

• Find each type of sub-shell in the shell
• Put the number of the shell it’s in in front of each. (This tells you how many of each sub-shell there are).
• Find the total number of electrons using:

no. of electrons in a sub-shell =

number of orbitals (1 (for s), 3 (for p) 5 (for d) or 7 (for f)) x max. no. of electrons in each orbital (2)

• Add the number of electrons of each type of sub-shell together, to get the total number of electrons in the shell (the energy level).

Question 10

1. What is an orbital?
2. What do you need to remember about orbitals within the same sub-shell?

Answer 10

1. a bit of space (a cloud) than an electron moves in.
2. Orbitals within the same sub-shell have the same energy.

Question 11

What happens if there are two electrons in an orbital?

Answer 11

If there are two electrons in the same orbital they have to ‘spin’ in opposite directions - this is called spin-pairing.

Question 12

What are the shapes of s and p orbitals?

Answer 12

• s orbitals are spherical
• p orbitals are dumbbell shaped - there are three types of p orbitals and they’re at right angles to one another.

Question 13

What is an electron configuration?

Answer 13

The number of electrons an atom or ion has, and how they are arranged.

Question 14

e.g. if neon has 10 electrons, how are these arranged in each sub-shell?

Answer 14

• 2 in the 1s subshell as an s sub-shell can only have one orbital and therefore a max. of two electrons:

orbitals in an s sub-shell (1) x no. of electrons in an orbital (2) = 1 x 2 = 2

• 2 in the 2s sub-shell, the second s sub-shell (NOT 2xs) as an s sub-shell can have a max. of 2 electrons.
• 6 in the 2p sub-shell as a p sub-shell can have 3 orbitals with 2 electrons.
• 2+2+6 = 10

Question 15

What is meant by the term electron configuration?

Answer 15

the no. of electrons an atom or ion has and how they are arranged.

Question 16

What are the 2 different ways youu can show electron configuration?

Answer 16

Question 17

What are the 3 rules for filling out electron configurations?

Answer 17

The Mg²⁺ ion only has 10 electrons (rather than 12, like a neutral atom of Mg) as it has lost two electrons.