Chapter 2-Atomic structure Flashcards
A
Mass #
Z
Atomic #
Anions
Gain (e-) to become negative (-)
Cations
Lose (e-) to become positive (+)
Isotopes
Atoms with the same # of protons and electrons but diff # of neutrons
Have similar chem properties (cuz it’s valence electrons that determine chem prop)
Ar (Relative atomic Mass)
(% Abundance)(mass)+…+…/100
How can Radioisotopes be made?
Exposing the natural element to flux of slow moving neutrons in nuclear reactor.
(Nucleus captures EXTRA neutron!)
Radioactive tracers rely on?
Fact that radioisotopes behave chemically (& biologically) the SAME as stable isotopes.
Nuclear Medicine (Thyroid glands % Iodine)
- Thyroid glands=absorbs iodine
- Activity can be measured by monitoring the increase in radioactivity of glands after taking drink containing traces of radioactive iodine [I(125) or I(131)]
- PET scanners detect abnormalities s.a growth of tumour etc.
Atomic Spectra (by decreasing Freq)
Radio waves/ Microwaves/ IR light/ Vis. L/ UV light/ X-rays/ gamma rays
Blue light has more____than red light
Energy
When an atom is excited by what happens to electrons?
The electrons gain energy and move to a higher energy level.
If atom excited by light what happens?
Light of particular wavelength corresponding to the Activation Energy = ABSORBED= leaves a black line in the continuous spectrum. (LINE ABSORPTION SPECTRUM)
What happens when electrons return to lower energy?
It must LOSE energy! By emitting light of a particular frequency = LINE EMISSION SPECTRUM
Equation of amt of energy lost by electron
Change in energy= (h)(v)
Where:
h = Plank’s constant = 6.63*10^-34 J
v = Frequency
Velocity equation
c = (v)(lambda) c = Velocity in vacuum (3*10^-8 m/s)
What happens to the lines in the spectrum as freq increases?
They will converge. Cuz the higher the energy level = the smaller the difference in energy between successive energy levels.
What is the limit of the convergence of the lines in the emission spectrum?
The energy required to completely remove the electron from the atom = IONISATION ENERGY
What does each series in an emission spectrum correspond to?
It corresponds to the transitions in which the electrons fall to a particular energy level.
Lyman series region of light
UV
Balmer series region of light
Visible light
Pauli exclusion principle
No 2 electrons in an atom can be in exactly the same state.
How many orbitals does the s,p,d sub-levels each contain?
s = 1 p = 3 d = 5
How many electrons does the s,p,d sub-levels each contain?
s = 2 p = 6 d = 10
‘Aufbau’ principle
Electrons in atoms ALWAYS adapt the lowest energy configuration possible. By filling in one sub-level COMPLETELY before the next.
Hund’s Rule
Sub-level orbitals are singly occupied as far as possble by electrons in the same spin.
Exceptions to the filling of 3d and 4s orbitals
When there’s a possibility of the 3d sub-level to be HALF or FULLY filled = takes PRIORITY over completely filling 4s sub-level.
Ionisation energy
The min amt of energy required to remove a mole of electrons from a mole of gaseous ATOMS to from a mole of gaseous IONS. (CATIONS)
Is Ionisation every exothermic or endothermic?
Exothermic.
Energy needed to remove negatively charged electrons from attraction of positively charged nucleus.
The charge on the nucleus of an atom is counteracted by? (3 things)
- Repulsion
- “Shielding” of electrons in filled inner orbitals
- Repulsion from other electrons in valence shell.
Effective Nuclear Charge (ENC)
The remaining nuclear charge in each energy level when the total nuclear charge is subtracted by the electrons in the different shells.
Why use the log scale for Ionisation energy?
Makes shell structure more obvious cuz if linear scale was used ALL the 1st ten ionisation energies would be v. close together.
Why is there a steady increase of successive ionisation energy for every element?
As more electrons removed = decrease in the electron-electron repulsion betw. electrons in valence shell.
What happens to ionisation energy going across a period?
Steady increase. cuz increase of nuclear charge of atoms within an energy level. As the electrons are added to the same energy level.
What happens to the ionisation energy going down a group.
Decreases.
Effective nuclear charge = relatively constant (extra nuclear charge = cancelled out by an extra filled electron shell)
Electrons lost = in successively higher energy level = further from nucleus.
Isoelectrons
Species that have the same electronic structure.
