Atomic structure & Electron structure

Question 1

Define relative formula mass.

Answer 1

weighted mean mass of an atom compared with 1/12th mass of an atom of carbon-12

Question 2

How to calculate relative formula mass

Answer 2

(isotopic mass x % abundance) / 100

Question 3

How are sub-shells organised?

Answer 3

shell 1 = s
shell 2 = s, p
shell 3 = s, p, d
shell 4 = s, p, d, f

Question 4

What is the order of increasing energy in the sub-shells?

Answer 4

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p

Question 5

How many electrons can an orbital hold?

Answer 5

2 electrons

Question 6

Sub-shells are split into atomic orbitals, what is an orbital?

Answer 6

a region within an atom that can hold up to 2 electrons with opposite spins

Question 7

What is a spin?

Answer 7

Property of particles, they can be thought of as rotating either clockwise or anti-clockwise

Question 8

If an orbital is filled with two electrons, would their spins be opposite?

Answer 8

Yes

Question 9

What do S-orbitals look like?

Answer 9

Sphere

Question 10

What do P-orbitals look like?

Answer 10

Dumbbell

Question 11

How many orbitals are in each sub shell?

Answer 11

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

Question 12

What is the max number of electrons in each sub shell (according to number of orbitals)?

Answer 12

number of orbitals (odd numbers) x2

s = 2
p = 6
d = 10
f = 14

Question 13

What is the trend between energy and distance from nucleus?

Answer 13

Sub shell lower in energy = closer to nucleus (more stable)

Question 14

How to work out number of electrons in a shell

Answer 14

2n^2

(n = shell number)

Question 15

How to write out electron configurations?

Answer 15

e.g. 2p^3

Big number = shell number
P = sub-shell
Small number = number of electrons in sub-shell

Question 16

How to work out noble gas configuration?

Answer 16

Look at noble gas in period above element you are looking at - use to shorten
e.g. Ni = [Ar] 4s^2 3d^8

Question 17

What are the exceptions (Cr-><-uc)

Answer 17

Copper and chromium would rather their last sub-shell be half full or full (more stable)

Cr = [..]4s^1 3d^5
Cu = [..]4s^1 3d^10

Question 18

Electronic configurations of ions

Answer 18

Positive = electrons removed from highest energy orbitals

Negative = electrons added to highest energy orbitals

Question 19

Are electrons removed from 4s before 3d?

Answer 19

Yes because removal occurs from highest energy level (shell furthest away from nucleus)

Question 20

What are the rules regarding arrangement of electrons in sub-shells?

Answer 20

• each orbital can hold max 2 electrons, each with opposite spins (opposite directions)
• electrons occupy orbitals singly where possible due to charge repulsion (only pair up when forced to)