Atomic Structure Flashcards
Name the 3 subatomic particles
Proton, neutron, electron
What is the relative mass of an electron
1/2000 or 1/1840
What letters do we use to represent mass number and atomic number
Mass number = M and Atomic number = Z
How is a positive ion formed
By losing electrons
What ion would be expected to be formed by an element in group 6
2- ion
What is the formula of the sulfate ion
SO42-
Write the chemical formula of calcium nitrate
Ca(NO3)2
Define isotope
Isotopes are atoms of the same element (same number of protons) with different numbers of neutrons
Calculate the number of neutrons in C12 and C14
6 in C12 and 8 in C14
Why do isotopes have the same chemical properties
Same number of electrons
Describe the atomic model proposed by JJ Thompson
Plum pudding model, sphere of positive charge with electrons dotted around
Describe the experiment of Rutherford where he discovered the nucleus
Fired alpha particles at gold foil and some deflected and a few bounced back showing small centers of positive charge
Describe the atomic model proposed by Bohr
Positive nucleus surrounded by electrons in defined shells
How could you calculate the mass of one atom of oxygen using its Ar of 16
16 divided by the Avagadro’s constant (6.022 x 10^23)
What is meant by relative atomic mass
Mean mass of atoms of an element relative to the mass of 12g of carbon 12
What are the 5 main stages in mass spectrometer
Vaporisation, Ionisation, acceleration, drift, detection
Write generic equations to show the ionisation of X in a mass spectrometer by electron impact and proton absorbtion.
e- +X (g) –> X+ (g) + 2e-
X + H+ ——> XH+
Write a generic equation to show the ionisation of X in a TOF mass spectrometer
H+ +X (g) –> XH+ (g)
What are the two methods of ionisation that could be used in a mass spectrometer?
electron impact and electrospray
Describe what happens during electrospray ionisation
Particles gain a proton
Compare the speed and kinetic energy of a lithium and potassium atom in TOF mass spectrometry
Speed of lithium faster than potassium. Both have same KE
What is meant by the molecular ion peak
The highest m/z value on the spectrum of a molecule, formed when the molecule does not break up
How do you work the RMM in a TOF mass How do you work the RMM in a TOF mass spectometer
Subtract one from the mass of the molecular ion
Why is m/z used in a mass spectrum not just mass
Because atoms can be doubly ionised and would be accelerated more quickly
How are ions detected in a mass spectrometer?
ions hit the detector and gain electrons, which causes a current to flow
How can you determine the number of ions hitting the detector at a m/z value?
The size of the current indicates how many ions of that m/z ratio are hitting the detector
Calculate the Ar of an element sample which is made up of 75% C12 and 25% C14
12.5
How many electrons can the s, p and d subshells each hold
s = 2, p = 6, d = 10
Write the electronic configuration of an element with 20 electrons
1s2,2s2,2p6,3s2,3p6,4s2
Write the electronic configuration of an elements with 24 electrons
1s2,2s2,2p6,3s2,3p6,4s1 3d5
Which two transition metal elements do not have a full 4s orbital
Chromium and copper
As a general rule which energy levels do electrons fill first?
Electrons fill orbitals in order from lowest energy to highest energy
Which subshell fills first 4s or 3d?
4s
From which subshell are electrons removed first during ionisation 4s or 3d?
4s
Into what orbitals would two electrons in a p subshell go?
Electrons fill orbitals singularly before pairing up
Fe has electron configuration [Ar] 4s2 3d6. what is the electron configuration of the Fe3+ ion
[Ar] 3d5
Define first ionisation energy
The energy required to remove one mole of electrons from one mole of atoms in the gaseous state
Write an equation to show the 1st ionisation energy of sodium
Na(g) ——> Na+(g) + e-
Write an equation to show the 4th ionisation energy of calcium
Ca3+(g) ——> Ca4+(g) + e-
Is ionisation energy exothermic or endothermic
Endothermic - requires energy
How does nuclear charge affect ionisation energy
Increasing nuclear charge increase ionisation energy as electrons harder to remove
How does 1st ionisation energy change down the group and give 2 reasons why
Decreases down group. Electrons further from nucleus so less attraction and more shielding so less attraction
Write an equation to show the third ionisation energy of nitrogen
N2+ –> N3+ + e-
Why do group 3 elements eg. Al, not fit the trend in increasing first ionisation energy across the period
Electrons removed from a p orbital which is further from the nucleus so less attraction so ionisation energy decreases
Why do group 6 elements eg. O, not fit the trend in increasing first ionisation energy across the period
Electrons removed from an orbital which contains two electrons which gives some repulsion so easier to remove. So ionisation energy decreases
