1. Atomic Structure And Periodic Table Flashcards
What is an isotope?
Isotopes are atoms with the same number of protos, but different number of neutrons
What is the relative isotopic mass?
Is the mass of an isotope compared to 1/12th of the mass of one atom of a carbon-12
What’s relative atomic mass?
the average mass of one atom compared to 1/12th of the mass of one atom of carbon-12
What’s relative molecular mass?
The average mass of a molecule compared to 1/12th of the mass of one atom of carbon-12
What can a mass spectrometer be used to determine?
all the isotopes present in a sample of an element and to therefore identify elements
What is the equation to work out the relative atomic mass if abundance % is used?
RAM = (isotopic mass x % abundance) / 100
What is the equation to work out the relative atomic mass if relative abundance is used?
RAM = isotopic mass x relative abundance / total relative abundance
What is the peak with the largest m/z on a mass spectra called?
the molecular ion
What are some real life examples of uses of mass spectrometers?
. planetary space probes so that elements on other planets can be identified
. drug testing in sport to identify chemicals in the blood
. quality control in pharmaceutical industry
. radioactive dating to determine age of fossils or human remains
What is the definition for first ionisation energy?
The first ionisation energy is the energy required when one mole of gaseous atoms forms one mole of gaseous ions with a singe positive charge
Write an equation for the first ionisation energy of hydrogen. include state symbols.
H (g) ——-> H+ (g) + e-
What is the definition for first ionisation energy?
The second ionisation energy is the energy required when one mole of gaseous ions with a single positive charge forms one mole of gaseous ions with a double positive charge
Write an equation for the second ionisation energy of titanium. include state symbols.
Ti+ (g) ———> Ti+2 (g) + e-
What are the 3 main factors that affect ionisation energy?
. the attraction of the nucleus (the more protons, the greater the attraction)
. the distance of the electrons from the nucleus ( The bigger the atom the further the outer electrons are from the nucleus and the weaker the attraction of the nucleus)
. shielding of the attraction of the nucleus ( an electron in an outer shell is repelled by electrons in complete inner shells, weakening the attraction of the nucleus)
What do the patterns in successive ionisation energies for an element inform us of?
information about the electronic structure for that element
Why are successive ionisation energies always larger?
. when the first electron is removed a positive ion is formed (1st IE)
. the ion increases the attraction on the remaining electrons and so the energy required to remove the next electron is larger
How are ionisation energies linked to electronic structure? (when looking at a graph, and there’s a big jump between numbers e.g 4 and 5)
. the fifth electron is in a inner shell closer to the nucleus and therefore attracted much more strongly by the nucleus than the fourth electron
. it also doesn’t have any shielding by inner complete shells of electron
What is periodicity?
A repeating pattern across a period
Why has helium the largest first ionisation energy?
. Its first electron is in the first shell closest to the nucleus and has no shielding effects from inner shells
. He has a bigger first ionisation energy than H as it has one more proton
Why do first ionisation energies decrease down a group?
As one goes down a group, the outer electrons are found in shells further from the nucleus and are more shielded so the attraction of the nucleus becomes smaller
Why is there a general increase in first ionisation energy across a period?
.As one goes across a period, the number of protons increases making the effective attraction of the nucleus greater.
. The electrons are being added to the same shell which has the same shielding effect and the electrons are pulled in closer to the nucleus
Why has Na a much lower first ionisation energy than Neon?
.Because Na will have its outer shell electron in a 3s shell further from the nucleus and is more shielded
. So Na’s outer electron is easier to remove and has a lower ionisation energy.
Why is there a small drop from Mg to Al?
. Al is starting to fill a 3p sub shell, whereas Mg has its outer electrons in the 3s sub shell
. The electrons in the 3p subshell are slightly easier to remove because the 3p electrons are higher in energy and are also slightly shielded by the 3s electrons
Why is there a small drop from Mg to Al?
. with sulphur there are 4 electrons in the 3p sub shell and the 4th is starting to doubly fill the first 3p orbital
. When the second electron is added to a 3p orbital there is a slight repulsion between the two negatively charged electrons which makes the second electron easier to remove
