The Atomic Structure Flashcards
What is the mass number?
The number of protons and neutrons added together
What is the atomic number?
The number of protons-also the number of electrons
What are isotopes?
Isotopes are atoms of the same element that have the same number of protons but different number of neutrons
What is common between isotopes?
Isotopes have similar chemical properties because they have the same electronic configuration
What are the different phases of a Time of Flight Mass Spectrometer?
- Ionisation
- Acceleration
- Ion drift
- Detection
What are the two different types of ionisation?
- Electron impact
- Electrospray
What are the steps for the electron impact ionisation?
- A sample is vaporised and is injected at a low pressure
- An electron gun fires high energy electrons at the sample
- An outer electron is knocked out of the sample
- This forms positive ions
What are the steps for the electro spray ionisation?
- The sample is dissolved in a volatile polar solvent.
- The sample is pumped through a hypodermic needle and at the tip, a high voltage is applied
- at the tip of the needle, the sample gains a H+ ion
- The sample is vapourised
What is the electron impact used for?
It is used for elements and substances with low formula mass. This method would cause larger molecules to fragment
What is the electrospray ionisation used for?
It is used for larger molecules and means that they won’t fragment.
What happens in the acceleration phase?
The positive ions are accelerated by an electric field
All the ions are given the same kinetic energy
The velocity of the particles depends on their mass
What happens in the ion drift?
In the ion drift, it is a vacuum and the particles drift along to the detector
The lighter ions travel faster compared to the heavier ions
allows separation of the sample
What happens at the detection?
The detector detects charged ions
the ions gain electrons from the negatively charged plate
The movement of the electrons creates a current
How do you calculate the relative atomic mass(RAM)?
RAM =∑ (isotopic mass*relative abundance)/total relative abundance
What is the current created proportional to?
The abundance of the isotope
What is relative mass?
The average mass of isotopes
How are electrons arranged around the nucleus?
Energy levels
What are energy levels divided up into?
Sub shells
What are the 4 sub shells?
s,p,d,f
What is the maximum number of electrons that each sub shell can contain?
s = 2 p = 6 d = 10 f = 14
Which block are the reactive metals?
S block
Which block are the transition metals?
D block
Which block are group 3 to 0?
P block
How are ions formed?
Ions are formed when atoms lose or gain electrons
What is the definition of isoelectric?
Isoelectric means different elements with the same configuration
What are some examples of isoelectric elements/ions?
N(3-) O(2-) F(-) Ne Na+ Al(3+) Mg(2+)
What happens when transition metals form ions?
they always lose the 4s energy levels before the 3d energy level
What is ionisation energy?
Ionisation energy is the amount of energy required to remove 1 mole of electrons from a mole of atoms in the gaseous state and is measured in kJmol(-1)
What happens to the ionisation energy the further away the outer orbital is from the nucleus?
The ionisation energy decreases as there is weaker force of attraction, so it is easier to remove the electron from the outer shell.
Why does group 4 only bond covalently?
Group 4 atoms can either lose or gain 4 electrons as they already have the outer shell half-full.
they bond covalently to share electrons
What are the 3 factors that affect ionisation energy?
- Distance from the nucleus
- Shielding
- Nuclear charge
How does distance affect ionisation energy(I.E)?
- The further away the orbital is, from the nucleus
- The weaker the force of attraction
- The lower the I.E needed
How does shielding affect the I.E needed?
- as the number of electrons between the nucleus and the outer electrons increases
- The weaker the force of attraction to the nucleus
- The lower the I.E needed
How does nuclear charge affect the I.E needed?
- The more protons there are than the electrons
- The more positively charged the nucleus
- The stronger the force of attraction
- The higher the I.E needed
What happens to the ionisation energy when in the same block?
e.g. p-block, s-block e.t.c
- The higher the number of protons
- The outer electrons are in the same sub-shell
- The stronger the force of attraction
- The higher the amount of I.E needed
What happens to the ionisation energy when jumping blocks?
e.g. s-block to p-block
- There is a new sub-shell (further away from the nucleus)
- The weaker force of attraction
- The lower the I.E needed
When happens to the ionisation energy during electron-pair repulsion?
- The electrons are already repelling each other
- They are easier to remove
- The lower the I.E needed
Why do you need more I.E to remove an electron from an ion?
- There are more protons than there are electrons
- The ion is positively charged
- There is a stronger force of attraction
- More I.E is needed
What is successive ionisation energy?
Successive ionisation energy is the energy needed to remove 1 electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions
How does successive ionisation energy help you determine which group an element is in?
The largest jump between 2 ionisation energies tells you which group the element belongs to.
If the largest jump in ionisation energy is between the first and the second ionisation energies, then the element is in group 1.
What is the trend in the first ionisation energies down a group in the periodic table?
The first ionisation energies decrease.
What is the trend in the first ionisation energies across a period in the periodic table?
The first ionisation energies generally increase.
What is the principal quantum number?
The principal quantum number is the relative overall energy of each orbital and the energy increases as the distance from the nucleus increases.
What is the relative mass and charge of a proton?
Relative mass - 1
Relative charge - +1
What is the relative mass and charge of an electron?
Relative mass - 1/2000
Relative charge -> -1
What is the relative mass and charge of a neutron?
Relative mass - 1
Relative charge - 0
Which subatomic particles decide the chemical properties of an element?
The number and arrangement of electrons
Why do physical properties of isotopes of an element differ?
Physical properties are dependant on the mass of the atom.
Where is most of the mass of an atom found?
In the nucleus
What can be found in the nucleus?
Protons and neutrons
What can mass spectrometry be used for?
- To identify elements
- To identify molecules
What is the electronic configuration of copper?
1s(2) 2s(2) 2p(6) 3s(2) 3p(6) 4s(1) 3d(10)
What is the electronic configuration of chromium?
1s(2) 2s(2) 2p(6) 3s(2) 3p(6) 4s(1) 3d(5)
Why do chromium and copper donate one of the 4s electrons to the 3d sub-shell?
- They become more stable
- Copper has a full outer shell
- Chromium has half of the outer shell full
What happens to the I.E between group 2 and 3?
The I.E drops due to the sub-shell structure
What happens to the I.E between group 5 and 6?
The I.E drops due to electron repulsion
Why does the successive I.E increase with each shell?
- Electrons are being removed from an increasingly positive ion
- There is less repulsion between remaining electrons
- Remaining electrons are held more strongly by the nucleus
What do big jumps in I.E show?
It shows an electron is being removed from a new sub-shell closer to the nucleus
How did John Dalton describe atoms as?
He described atoms as solid spheres and different elements are made up of different spheres
What did J.J Thomson discover in 1897?
The electron
The plum pudding model was created
Which famous experiment in 1909 did Ernest Rutherford and his students Hans Geiger and Ernest Marsden conduct?
They fired alpha particles at a thin gold foil
What did the gold foil experiment show?
Most of the particles passed straight through the gold with very few being deflected backwards
What did Rutherford conclude from the experiment?
- The plum pudding model couldn’t be right and he developed the nuclear model
- The atom contained a tiny positively charged nucleus and surrounded by electrons
- Most of the atom was empty space
What did Niels Bohr propose about the model of the atom?
Electrons exist in shells or orbitals
What happens when electrons move between shells?
Electromagnetic radiation(fixed energy or frequency) is emitted or absorbed
Why did the Bohr model replace the nuclear model?
The Bohr model fitted experimental observations of radiation emitted and absorbed by atoms
What did scientists discover which meant that the Bohr model wasn’t quite right?
Scientists discovered not all electrons in a shell have the same energy
-They discovered sub-shells
Why is the Bohr model of the atom still useful today?
- It is simple
- It explains many experimental observations like bonding and ionisation energy trends