chem topic 1 Flashcards
(18 cards)
what is an isotope?
atoms of same element with same number of protons but different number of neutrons
relative isotopic mass?
mass on one atoms isotope relative to 1/12 the mass of an atom of the isotope carbon -12
relative atomic mass
average mass of an atom of an element relative to 1/12 the mass of a carbon 12 atom
how does mass spectrometry
- vaporise atom by vacuum
- ionised by high energy electron gun
- positive plates accelerate electron
- ion deflected by magnetic field
large deflection = low mass, high charge
little deflection = high mass, low charge
periodicity
repeating patterns of properties across a period
1st ionisation energy
energy required to remove 1 mol of gaseous electron from 1 mol of gaseous atom to make 1 mol of gaseous 1 + ion
factors affecting ionisation energy (3)
atomic radius / ionic radius
nuclear charge
shielding
trend across period in ionisation energies?
N.C increases, shielding constant so radius decreases = greater attraction between valece e and nucleus so more energy required
what is shielding
affect of core e reducing attraction between nucleus and valence e
effective nuclear charge?
attraction felt by valence electrons
N.O protons -N.O core electrons
exceptions to first ionisation energies in period 2
B has lower IE as electron now being removed from 2p subshell, further from the nucleus than the 2s subshell
O has lower ionisation energy as repulsion between paired e in one of the 2p subshells reduces attraction to nucleus
successive ionisation energies
energy required to remove successive electrons from shells in atom
trend in successive ionisation energy
general increase as e are being removed from ion with increasing effective nuclear charge so radius is smaller and there’s greater attraction between valence e and nucleus
big jumps due to e now being removed from shell closer to nucleus= less radius and less shielding
1st ionisation energy trend down group
increased atomic radius and shielding outweighs increasing nuclear charge so less attraction between valence e and nucleus
what happens when a gas is heated
e is promoted to higher energy level when excited by heat
e then relaxes back down emitting a photon of energy
Cr electron config
1S2 2S2 SP6 3S2 3P6 4S1 3D5
Cu electron config
1S2 2S2 2P6 3S2 3P6 4S1 3D10
melting point trends across period
Li to B = metallic bonding between metal ions and sea of e (B has higher MP as B3+ has 3e- released whereas Li only goes to Li+ and 1 electron released)
C Giant covalent structure and covalent bonds
N - F = weak intermolecular forces
Ne = no intermolecular forces
