Atomic Structure (3.1.1-Phys.)

Question 1

Define relative atomic mass

Answer 1

Ave. mass of an atom compared 1/12 th the mass of an atom of C-12

Question 2

What is the atomic number?

Answer 2

The number of protons.

Question 3

What are energy levels?

Answer 3

Shells

Question 4

Why are atoms with more energy levels more reactive?

Answer 4

Valence electron

• Further from nucleus
• Easier to remove

Question 5

How do you calculate relative atomic mass

Answer 5

∑(isotope abundance x mass number)/100

Question 6

What is a mass spectrometer?

Answer 6

Used to accurately determine the Ar or molecular mass

Question 7

How do you ionise small molecules? [ToF]

Answer 7

M(g) + e- ——–> M+(g) + 2e- (electron gun)

A high energy electron is fired at a small molecule, knocking off an electron, resulting in a positive charge.

Question 8

How do you ionise large molecules? [ToF]

Answer 8

M(g) + H+ ——-> MH+(g) [mass increased by 1]
(electrospray ionisation)
A proton is given to the sample which increases the mass by 1, making its charge positive

Question 9

What is the second stage of ToF?

Answer 9

Acceleration

Question 10

What occurs in stage 2 of ToF?

Answer 10

• Positive ions attracted to negatively charged plates
• Focused into a beam
• All have the same kinetic energy

Question 11

What is stage 3 of ToF?

Answer 11

Ion Drift

Question 12

What occurs in stage 3 of ToF?

Answer 12

• lighter ions move more quickly because they have same KE,

- Reach detector first (KE=1/2mv^2)

Question 13

What is stage 4 of ToF?

Answer 13

Detection

Question 14

What occurs in stage 4 of ToF?

Answer 14

• Ions hit the detector and an electron is added
• size of current is proportional to the abundance
• mass/charge

Question 15

How is the graph of abundance labelled?

Answer 15

• x– mass (m)/charge (z)

- y– relative abundance

Question 16

Why would isotopes of one element have the same chemical properties?

Answer 16

They would have the same electron configuration

Question 17

How many electrons does one orbital hold?

Answer 17

2 electrons

Question 18

What is the order of sub levels of energy levels?

Answer 18

1s, 2s, 2p, 3s, 3p, (4s, 3d), 4p, 4d, 4f

Question 19

How many orbitals are contained in ‘s’?

Answer 19

1

Question 20

How many orbitals are contained in ‘p’?

Answer 20

3

Question 21

How many orbitals are contained in ‘d’?

Answer 21

5

Question 22

What are the two exceptions when writing out electron configurations?

Answer 22

Cr and Cu, only ONE electron in their 4s orbital

Question 23

What is the rule surrounding the ‘3d’ and ‘4s’ orbitals?

Answer 23

When writing out they can be written in either order, ‘3d’ has higher energy, but when removing an elecron you remove it from the ‘4s’ orbital.

Question 24

Define first ionisation energy

Answer 24

The energy required to remove one mole of electrons from one mole of gaseous atoms
M(g) ———> M+(g) + e-

Question 25

What factors affect IE?

Answer 25

1) Nuclear charge (no. protons)
2) Atomic radius (closeness to the nucleus)
3) Shielding (more electons btwn nucleus and outer e-)

Question 26

What is the general trend of 1st I.E. across a period with reasons?

Answer 26

1st IE generally increases across a period,

• nuclear charge increases
• atomic radius decreases

Question 27

What is the first ‘blip’ in the rising graph of 1st IE?

Answer 27

e. g. period 3
- Mg, one 3s e- is being removed
- Al, one 3p e- is being removed
- Al has lower 1st IE because 3p e- in Al is further from the nucleus and has higher energy than 3s e- in Mg

Question 28

What is the second ‘blip’ in the 1st IE graph?

Answer 28

e.g. period 3
- P has 3 e- in its 3p orbital (all in separate orbitals)
- S has 4 e- in its 3p orbital (2 in one orbital)
In S, the electron being removed experiences mutual repulsion from being part of a pair of electrons in one 3p orbital, so it requires less energy to remove.

Question 29

Why is 2nd IE > 1st IE?

Answer 29

More energy is required because its closer to the nucleus (lower ionic radius) and there may be more shielding. [+ve ion not neutral atom]

Question 30

Why is 3rd IE > 2nd IE?

Answer 30

e- from lower main energy level is closer to the nucleus, less shielded.

Question 31

Describe the trend of IE down group 2

Answer 31

• General trend is decrease in IE
• Outer electron is in a level that gets further from the nucleus
• Nuclear charge increases- though it is CANCELLED OUT by electron shielding from lower energy levels