3.1.1: Atomic Structure

Question 1

What is the charge of an atom?

Answer 1

neutral (0)

positively charged nucleus with negative electrons orbiting

Question 2

What is the definition of Relative Atomic Mass (Ar)?

Answer 2

the average mass of an atom of an element where C12= 12

Question 3

Charge and Mass of all the fundamental particles

Answer 3

charge mass
Protons: +1 1
Neutrons: 0 1
Electrons: -1 1/1836

Question 4

What’s an isotope?
Name the similarities and differences between them

Answer 4

What?: An atom with the same number of protons (atomic number) but different number of neutrons (mass number)
- They have similar chemical properties due to same no. of electrons and arrangement
- They have a different density and diffusion rate due to different mass no.

Question 5

What’s the basic structure of an atom (including subshells)

Answer 5

1s22s22p63s23p64s23d104p6

Question 6

What are the orbital no. and maximum electrons of each subshell?

Answer 6

s- 1 orbital, 2 max. electrons
p- 3 orbitals, 6 max. electrons
d- 5 orbitals, 10 max. electrons
f- 7 orbitals, 14 max. electons

when an ion loses electrons, it comes from the 4s shell

Question 7

What is the max. electron no. of each shell?

Answer 7

1st-2 electrons
2nd- 8 electrons
3rd- 18 electrons
4th- 32 electrons

each orbital holds 2 electrons

Question 8

What is ionisation energy?

Answer 8

A measure of the engery needed to pull a particular electron away from the attraction of the nucleus.

Question 9

What is the pattern of ionisation energy across the periodic table?

Answer 9

• increases across and upwards
• electronegativity is proportional to i.e.

Question 10

What would ionisation energy look like on a graph?

Answer 10

• starts from outer most electron
• small jump if move across subshell
• larger jump if move across shell
• closer to nucleus the electron, the more ionisation energy needed to remove the electron due to the stronger attraction the electrons have

Question 11

What’s a successive ionisation energy?

Answer 11

The energy needed to remove one electron after another. e.g. first i.e. goes to 2nd i.e.

Question 12

What’s the general trend in 1st ionisation energy?

Answer 12

• increases as you go along a period
• as proton no. and nuclear charge increases so there’s more attraction acting on electrons due to opposing charges
• electrons are added to same shell so the outer shell is drawn inwards towards nucleus
• same shell no.= similar shielding but more nuclear charge

Question 13

What are examples of the exceptions to patterns in first ionisation energy?

Answer 13

• paired electrond in subsbells as the electrons have the ssme charge so they repel each otber, making it easier to lose an electron, lowering i.e. (e.g. oxygen<nitrogen)
• a single, unbonded electron takes more i.e. as more nuclear charge acts on one single electronrather than a pair so there’s more opposing charge

Question 14

What is Time of Flight Mass Spectometry (ToFMS) used for?

Answer 14

this is a powerfyl analysis method used to:
- find abundance and mass of each isotope in an element to find relative atomic mass (Ar).
- find relative molecular mass of molecule substances

Question 15

What are the 4 steps of ToFMS?

Answer 15

• ionisation
• acceleration
• flight tube
• detection

Question 16

ToFMS

1.IONISATION (e.i.)

Answer 16

electron impact:
- an electron is knocked off each particle by high-energy electrons to form 1+ ions
- positive ions are accelerated by a negative electric plate
- used for low formula mass species
- forms ions (molecular ions)
X(g)+e- -> X+(g)+2e-

SAMPLE NEEDS TO BE GAS

Question 17

ToFMS

1.IONISATION (es)

Answer 17

electrospray:
- hypodermic needle attatched to positive terminal of high voltage power supply
- particles gain a proton as they leave the needle, turning into a fine spray
- positive ions are accelerated by negative electric plate
- used for high formula mass species
- increases mass:charge ratio by 1
X(g)+H+ -> XH+

sample needs to be dissolved in volatile solvent

Question 18

ToFMS

2.ACCELERATION

Answer 18

• positive ions accelerated using negative electric plate
• all ions have the same kinetic energy so velocity depends on mass/ Ar of each ion
• velocity of each particle (KE=½mv²)
• lighter particles have faster velocity than heavy ones

Question 19

ToFMS

3.FLIGHT TUBE

Answer 19

time= distance÷velocity
t=d×√(m/2KE)
- ion set off on flight tube at the same time
- lighter ions travel faster and begin to seperate out, reaching the detector first
-

ion drift- ions sperate out

Question 20

ToFMS

4.DETECTION

Answer 20

• positive ions hit negatively charged electric plate
• when they hit the detector plate, positive ions are discharged by gaining electrons from the plate
• this generates a movement of electrons so an electric current is measured
• the size of the current gives a measure of ions hitting the plate