topic 1: atomic structure and the periodic table Flashcards
structure of atom
- protons and neutrons in nucleus
- electrons in orbitals
rel charge proton
+1
rel mass proton
1
rel charge neutron
0
rel mass neutron
1
rel charge electron
-1
rel mass electron
1/1836
atomic number
- number of protons in nucleus of atom
- Z
mass number
total number of protons and neutrons in nucleus of atom (also known as nucleon number)
- symbol A
isotopes
same number of protons but different number of neutrons
properties of isotopes
- similar chemical properties but different physical properties
why do isotopes have similar chemical properties (2)
- same electron configuration
- same number of outer shell electrons so react similarly
relative isotopic mass
mass of one atom of an isotope relative to the mass of 1/12 of a carbon-12 atom
relative atomic mass
MEAN mass of an atom relative to the mass of 1/12 of a carbon-12 atom
chlorine ATOM mass spec
- 2 molecular ion peaks as exists as TWO ISOTOPES
-35 Cl and 37 Cl - peak heights ratio is 3:1 as abundance of 35Cl is 3* that of 37 Cl
diatomic chlorine molecule mass spec
-3 molecular ion peaks
- 35Cl+35Cl
-35Cl + 37Cl
-37Cl + 37Cl
RATIO of peaks: multiply probability of each; eg for 35, 35 3/4*3/4
one BROMINE atom mass spec
- 2 isootopes
- so 2 molecular ion peaks
-79Br and 81 Br - 1:1 abundance
diatomic bromine moleculemass spec
- 3 molecular ion peaks
- 79Br, 79Br
-79Br,81Br
-81Br,81Br
peak with highest m/z value…
molecular ion peak which gives info about MOLECULAR MASS
FIRST ionisation energy
amount of energy required to remove one mole of electrons from one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
first ionisation energy of calcium
Ca(g) -> Ca+(g) + e-
second ionisation energy
energy required to remove one mole of electrons from one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions
second IE calcium
Ca+(g) -> Ca2+(g) + e-
why do successive ionisation energies increase (generally)
- when an electron is removed, a positive ion is formed
- less electrons for same number of protons
- larger effective nuclear charge- STRONEGER ES ATTRACTION (decreasing p to e ratio)
- more energy required
shape of s orbital
spherical (draw a circle)
shape of p orbital
infinity sign (facing upwards)
what is an orbital
a region within an atom that can hold up to 2 electrons with opposite spins
IE across period
increases
IE down group
decreases
IE across period explanation
- increases
- nuclear charge increases
- atomic radius decreases as stronger attraction, so distance decreases
- CONSTANT shielding as electrons added to same shell
- more energy needed to remove an electron