1.1 Atomic Structure Flashcards
Which letter is used to represent the atomic number of an atom
Z
What does the atomic number tell us about an element
Atomic number = number of protons in an atom
What letter represents mass number
A
How is the mass number calculated
Mass number = number of protons + number of neutrons (total number of nucleons)
Define relative atomic mass
Average mass of all isotopes of an element compared to 1/12 the mass of an atom of carbon 12
What are isotopes of an element
Different forms of the same element, containing the swim number of protons but different numbers of neutrons. They still have the same chemical properties
How many orbitals and electrons do these shells contain
A 1s B 2p C 3s D 3d E 4s
1s - 1 orbital 2 electrons 2p - 3 orbitals 6 electrons 3s 1 orbital 2 electrons 3d 5 orbitals 10 electrons 4s 1 orbital 2 electrons
Does 3d or 4s have a higher energy
3d
What is an orbital
A region around the nucleus that can hold up to two electrons
What would be the relationship between 2 electrons in the same orbital in terms of their spin
Have opposite spin as repel each other as both negative
Explain why chromium does not fit the trend for electronic configuration
It only has one electron in its 4s orbital before filling 3d
Explain why copper does not for the trend for electronic configuration
It only has one electron in its 4s orbital before filling 3d
What are the two types of ionisation for a mass spectrometer? How do they differ?
Electron impact: electron gun (hot wire filament with current through it emitting electrons) knocks off one electron from each particle to form 1+ MOLECULAR IONS (these ions fragment)
Electrospray: sample dissolve in volatile solvent (e.g. water or methanol) and injected through a fine hypodermic needle to give an aerosol. Needle attached to positive terminal of a high-volatile power supply and particles gain a proton from the solvent as they leave the needle, producing XH+ ions (+1 charge and mass of Mr +1). (ions rarely fragment)
When would you use the different types of ionisation in a mass spec?
Electron impact used for organic or inorganic molecules with a low formula mass
Electrospray used for substances with a higher molecular mass including biological molecules e.g. proteins
Describe how a time of flight mass spectrometer works
Acceleration- positive ions attracted towards a negatively charged plate.
Ion drift - ions pass through hole in a plate, form a beam with constant kinetic energy, travel along tube to detector. Time of flight is therefore directly proportional to the square root of mass
Detection- positive ions pick up electrons, current flows, M/Z value and time of flight recorded. Largest current from most abundant ions
