Topic 1 - Atomic Structure and Periodic Table Flashcards
What is an isotope ?
Atoms of the same element with a different number of neutrons but the same number of protons
What is relative atomic mass? (Ar)
the weighted mean mass of an atom of an element compared to 1/12th of the mass of an atom of carbon-12
What is relative isotopic mass?
mass of an atom of an isotope compared to 1/12th of the mass of an atom of carbon-12
What is relative molecular mass (Mr)
average mass of a molecule compared to 1/12th of the mass of an atom of carbon-12
What are orbitals, subshells and quantum shells ?
quantum shells = the energy levels surrounding nucleus
subshell = (in quantum) path taken by electrons as moves around nucleus
orbitals = (in subshell) most probable regions of an electron within a shell
How many orbitals and electrons can each subshell hold ?
s subshell
- 1 orbital
- 2 electrons
p subshell
- 3 orbitals
- 6 electrons
d subshell
- 5 orbitals
- 10 electrons
f subshell
- 7 orbitals
- 14 electrons
How many electrons in an orbital ?
2 electrons
what is spin-pairing
when electrons in the same orbital have to ‘spin’ in opposite directions
what is the shape of s-orbitals?
sphere
what is the shape of p-orbitals
dumbell
Write the order of electron configuration when 3d is not full
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² ( eg. 3d⁴ )
What part of the periodic table is the s-block
Group 1 and Group 2
What part of the periodic table is the p-block
Group 3 to Group 0
What part of the periodic table is the d-block
transition metals
Explain the exception of chromium and copper in terms of electronic configuration ? (write one out)
- they donate one of the 4s -electrons to the 3d subshell
- more stable with full or half full 3d subshell
chromium (Cr) :
1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹
copper (Cu) :
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹
How does emission spectra support the idea of quantum shells
electron only exist in fixed orbits/shells
each shell has a fixed energy
when an electron moves between shells (gets excited) electromagnetic radiation is emitted or absorbed
energy of shells = fixed therefore radiation has fixed frequency
emission spectra show frequencies of light released
what is ionisation
the removal of one or more electrons
what is first ionisation energy
energy needed to remove one electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
what 3 factors affect ionisation energy and how
- nuclear charge - more protons = stronger attraction
- electron shells - attraction falls rapidly with distance
- shielding =- number of electrons increases between outermost and nucleus = less attraction/pull
what is the trend in ionisation energy
decreases down a group
increases across a period
what is successive ionisation energy
when you remove an additional electron
how does successive ionisation energy show shell structure
within a shell successive ionisation energies increase and more +ve ion = less repulsion
big jumps = new shell
what is the trend for atomic radius
decreases across a period
EXPLAIN the trend for atomic radius
number of protons increases = stronger pull to outer electrons
added electrons don’t affect as all added to same energy level across the period
Why is there a drop in ionisation energy between G2/G3 rather than an increase ? (use example of magnesium and aluminium)
magnesium :
1s² 2s² 2p⁶ 3s²
aluminium:
1s² 2s² 2p⁶ 3s² 3p¹
- Al outermost electron slightly higher energy level = further away from nucleus
- 3p orbital has additional shielding
both factors = enough to override effect of nuclear charge
Why is there a drop in ionisation energy between G5/G6 ? (use example of phosphorous and sulfur)
phosphorous:
1s² 2s² 2p⁶ 3s² 3p³
sulfur:
1s² 2s² 2p⁶ 3s² 3p⁴
shielding/distance = identical
therefore drop = electron repulsion
phosphorus - outermost removed from single occupied orbital
sulfur - removed from orbital with 2 electrons
