Topic 1: Atomic Structure and Periodic Table Flashcards
What is an atom?
- consists of a tiny nucleus containing protons and neutrons
- surrounded by electrons which make up the majority of the volume of the atom
Define isotopes
- Isotopes are atoms of the same element that have the same number of protons, but different numbers of neutrons
Define relative isotopic mass
Relative isotopic mass is the mass of one atom of an isotope compared to one-twelfth of the mass of one atom of carbon-12
- E.g. 35Cl ‘s isotopic mass is 35 (equal to the mass number)
Define relative atomic mass (Ar)
- Relative atomic mass of an element is the weighted average mass of an atom of an element compared to one twelfth the mass of one atom of carbon-12
Define relative molecular mass (Mr)
- Relative molecular mass is the average mass of a molecule compared to one twelfth of the mass of one atom of carbon-12
Define relative formula mass (Mr)
Relative formula mass is the average mass of the formula units of a ionic compound compared to one twelfth of the mass of one atom of carbon-12
What is mass spectrometry?
- measures the masses of atoms and molecules
- produces positive ions that are deflected by a magnetic field according to their mass-to-charge ration (m/z)
- also calculates relative abundance of each positive ion
Use of mass spectrometers
- drug testing in sports
- quality control in pharma
- radioactive dating to determine age of fossils or human remains
- space probes to identify elements on other planets
How do you work out the relative atomic mass from a mass spectra graph?
- multiply each relative isotopic mass by its relative isotopic abundance and add up the results
- divide by the sum of the isotopic abundances
What is the M+1 peak?
- seen when analysing organic compounds with large masses
- molecular ion peak + 1 due to the small percentage of carbon-13 present
Where do electrons move?
- electron move around the nucleus in quantum shells, also known as energy levels
- these shells are given numbers as principal quantum numbers
Do electron shells nearer or further away from the nucleus have greater energy?
- further away
Describe the electron shells in more detail
- shells contain different types of subshell
- these have different number of orbitals, which can hold up to 2 electrons
How many orbitals are there in subshell s and therefore how many electrons can it hold max?
- 1 orbital
- 2 electrons
How many orbitals are there in subshell p and therefore how many electrons can it hold max?
- 3 orbitals
- 6 electrons
How many orbitals are there in subshell d and therefore how many electrons can it hold max?
- 5 orbitals
- 10 electrons
How many orbitals are there in subshell f and therefore how many electrons can it hold max?
- 7 orbitals
- 14 electrons
Which sub shells are in the 1st electron shell?
- 1s
Which sub shells are there in the second shell?
- 2s
- 2p
Which subshells are there in the third shells?
- 3s
- 3p
- 3d
Which sub shells are in the 4th shell?
- 4s
- 4p
- 4d
- 4f
What are orbitals?
- orbitals is the space that an electron moves in
- orbitals within the same subshell have the same energy