Flashcards in Atomic Structure Deck (44):
What are atoms made up of?
Protons, neutrons and electrons.
What is the relative mass and relative charge of the sub-atomic particles?
Protons - relative mass, 1. Relative charge, +1.
Neutrons - relative mass, 1. Relative charge, 0.
Electrons, relative mass, 1/2000. Relative charge, -1.
Where in an atom will you find electrons?
They whizz around the nucleus in orbitals.
What takes up most the volume of the atom?
Where is most of the atoms mass found?
In the nucleus.
Why is relative mass and charge used for sub-atomic particles?
Because the mass and charge of the particles is really small so relative mass and relative charge is used instead.
What does the mass number show?
The total number of protons and neutrons.
What does the atomic number show?
The number of protons in the nucleus. It identifies the element as all atoms of the same element have the same number of protons.
How are ions formed?
By losing or gaining electrons.
What are isotopes?
Isotopes of an element are atoms with the same number of protons but different numbers of neutrons.
What decides the chemical properties of an element? W
The number and arrangement of electrons.
Why do isotopes have the same chemical properties?
They have the same electron configuration so they have the same chemical properties.
Why do isotopes have different physical properties?
Isotopes of an element have slightly different physical properties because physical properties depends on the mass of the atom and neutrons change the weight of the atom.
Define relative atomic mass, Ar.
The average mass of an atom of an element on a scale where an atom of carbon-12 is 12.
Define relative isotopic mass.
The mass of an atom of an isotope of an element on a scale where an atom of carbon-12 is 12.
Define relative molecular mass, Mr.
The average mass of a molecule on a scale where an atom of carbon-12 is 12.
Why is relative atomic mass not usually a whole number?
Relative atomic mass is an average so it’s not usually whole number.
What can a mass spectrometer tell you?
It can tell you the relative atomic mass, relative molecular mass and relative isotopic abundance
What are the four stages of a time of flight mass spectrometer?
Ionisation, acceleration, ion drift and detection.
What happens during the ionisation stage of a mass spectrometer?
There are two ways of ionising your sample:
-electrospray ionisation. This sample is dissolved and pushed through a small nozzle at high pressure. A high voltage is applied to it, causing each particle to gain a H+ ion. The sample is turned into a gas made up of positive ions.
-electron impact ionisation. The sample is vaporised and an ‘electron gun’ is used to fire high energy electrons at it. This knocks one electron off each particle so they become +1 ions.
What happened during the acceleration stage of a mass spectrometer?
The positively charged ions are accelerated by an electric field so they all have the same kinetic energy. (This means lighter ions will end up moving faster than the heavier ions)
What happens during the ion drift stage of a mass spectrometer?
The ions enter a region with no electric field so they will all just drift through it. Lighter ions will drift through faster than heavier ions.
What happens during the detection stage of a mass spectrometer?
Because ions that have a lower mass/charged ratio travel at higher speeds in the drift region, they reach the detector in less time than ions with a higher mass/charge ratio. The detector detects charged particles and a mass spectrum is produced.
How do you calculate the relative atomic mass (Ar) of an element from a mass spectrum?
For each peak multiply the % abundance (Y axis) by the relative isotopic mass (x axis) to get the total mass for each peak.
Add up all these masses
Divide by the sum of the relative abundance (should be 100 if % but might not be %)
What are electron shells made up of?
Sub-shells and orbitals.
Each shell is given a number called ...
The principal quantum number.
How many electrons can an orbital hold?
Each orbital can hold up to 2 electrons.
Which direction do the two electrons in each orbital spin?
They spin in opposite directions.
How many orbitals and what is the maximum number of electrons in an s sub-shell?
How many orbitals and what is the maximum number of electrons in an p sub-shell?
How many orbitals and what is the maximum number of electrons in a d sub-shell?
How many orbitals and what is the maximum number of electrons in a f sub-shell?
What are the rules to follow when working out electron configuration?
Electrons fill up the lowest energy sub - shells first. (4s is lower than 3d)
Electrons fill orbitals singly before they share.
When transition metals form ions do they lose their electrons from 4s before 3d?
What is the electron configuration of chromium? And why?
1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^5
Because it is more stable with a half full s and d sub-shell.
What is the electron configuration of a copper atom? And why?
1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^10
Because it is more stable with a half full s sub-shell and full d sub-shell.
Why are group 0 atoms unreactive?
They have completely filled s and p blocks so don’t gain, lose or share electrons - full sub-shells make them inert.
What is ionisation?
Ionisation is the removal of one or more electrons.
Define the first ionisation energy.
The energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.
Is ionisation an exothermic or endothermic reaction?
Endothermic as energy needs to be put in to ionise an atom or molecule.
Write and equation for the first ionisation of oxygen.
O(g) -> O+(g) + e-
What are the 3 factors affecting ionisation energies?
Distance from nucleus
How does nuclear charge affect ionisation energy?
The more protons there are in the nucleus, the more positively charged the nucleus is and the stronger the attraction for the electrons so it’s harder to remove electrons to form + ions and easier to gain electrons to form - ions.