Physical Chapter 1: Atomic Structure Flashcards
What subatomic particles make up atoms?
Protons, Electrons, and Neutrons
Where is most of the mass of an atom?
In the nucleus
What part of the atom makes up most of the volume?
Orbitals
What is the relative charge of an electron?
-1
What is the relative charge of a proton?
+1
What letter represents the mass number?
A
What letter represents proton number?
Z
What does the mass number represent?
Protons + Neutrons
What does Atomic number represent?
Number of protons
What is the relative mass of an electron?
1/2000
(negligible)
How are positive ions formed?
Atoms lose electrons
How are negative ions formed?
Atoms gain electrons
What is the relative mass of protons & neutrons?
1
What is an isotope?
Atoms with the same number of protons & electrons but different numbers of neutrons
Why do isotopes have the same chemical properties?
They have the same electron configuration
Why do isotopes have slightly different physical properties?
Physical properties tend to depend on the mass of an atom - isotopes have diferent mass
What was the order of atomic models?
Dalton Model - solid spheres
Plum Pudding Model
Rutherford model
Bohr Model
Refined Bohr model
What was the ‘solid sphere’ model?
All atoms are solid spheres, and different spheres make up different elements.
What was the ‘Plum Pudding’ model?
Electrons stuck in a large positively charged ball of ‘pudding’
What was the Rutherford Model?
Most of the atom is empty space, positively charged nucleus is surrounded by a ‘cloud’ of electrons.
Discovered by the alpha particle experiment
What was the Bohr Model?
Electrons exist in shells or orbitals of fixed energy.
Discovered via experimental observations of radiation emitted.
What was the refinement made to the Bohr model?
Electrons exist in sub-shells, not just shells.
Discovered due to electrons in the same shell not having the same energy.
What is the definition of relative mass?
The mass of one mole of an atom comapred to 1/12 Carbon-12.
(can be used as Relative molecular & relative isotopic mass as well)
How do you measure relative mass?
Mass spectrometry
What are the 4 stages of mass spectrometry?
Ionisation
Acceleration
Ion Drift
Detection
How does Ionisation work in TOF Mass spectrometry?
There are two methods:
Electrospray Ionisation - A sample is dissolved & pushed through a small nozzle at high pressure. A high voltage is applied to it, adding an H+ ion to each sample, forming a gas of positive ions.
Electron impact ionisation: The sample is vaporised & an electron gun fires electrons at it, knocking electrons off of it & forming +1 ions.
How does acceleration work in TOF Mass spectrometry?
The positievly charged ions are accelerated by an electric field so that they all have the same kinetic energy.
This means the lighter ions will move faster.
How does Ion Drift work in TOF Mass spectrometry?
The ions enter a region with no electric field, so they just drift through it. Lighter ions will drift through faster than heavier ions.
How does Detection work in TOF Mass spectrometry?
Lighter ions travel at higher speeds, so they’re detected first. The Detector detects charged particles first, and a mass spectrum is produced.
What is the difference between mass spectra of electron impact ionisation & electrospray ionisation?
Electrospray ionisation mass spectra will have peaks that are one unit greater than the relative mass of each isotope.
Electron impact ionisation mass spectra have peaks that are equal to the relative mass of each isotope.
What is TOF Mass Spectrometry?
Time of Flight Mass Spectrometry
How do you find Relative atomic mass from a mass spectrum?
Multiply every relative isotopic mass by its percentage abundance & add them together, then divide by 100
What is the order in which sub-shells fill?
How are orbitals filled?
Electrons fill orbitals singly before they fill up doubly.
What are the two exceptions to the rule regarding transition metal electron structures?
Chromium & Copper donate 4s electrons to the 3d sub-shell, as it’s more stable.
When they become ions, they lose the 4s electrons before their 3d electrons.
What determined chemical properties?
Electron Structure
What is ionisation energy?
The energy needed to remove an electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous ions
What are the 3 factors affecting ionisation energy?
Nuclear Charge - Greater nuclear charge means greater Ionisation energy
Atomic Radius - Greater atomic radius means lower ionisation energy
Shielding - greater shielding means lower ionisation energy
What is the definition of second ionisation energy?
The energy needed to remove one electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions
What is the trend of successive ionisation energies within each shell?
They increase
What causes a large increase in ionisation energy?
Change in shell
What is the trend in ionisation energy down a group?
What causes this?
Decreases
Greater shielding as you go down the group, as well as greater atomic radius
What is the trend in ionisation energy across a period?
What causes this?
Increases
There is stronger nuclear attraction, whereas atomic radius & shileding barely change
WHy is there a drop in ionisation energy across a period between groups 2 & 3?
It shows sub-shell structure: the p orbital has a slightly higher energy, so is further away from the nucleus, as well as experiencing slightly higher shielding from the s electrons.
Why is there a drop in ionisation energy between groups 5 & 6?
Electron repulsion - Shileding is identical, but the electron is removed froma paired orbital, meaning it’s easier to remove due to electron repulsion.
