Periodicity Flashcards
Ionisation energy
Periodicity
Repeating pattern of properties shown across different periods within their position in the periodic table
Group 1
Alkalis, less dense than water, fizzing, floats, dissolve
Why do atoms of elements in a group have similar properties
Same number of outer shell electrons, same electron configuration
Group 1 reactivity
Reactivity increases as you go down the group due to more shells,
easier to lose electrons,
weaker attraction to nucleus, less atomic radius
Ionisation energy
Energy required to remove one electron from each atom in a mole of gaseous atoms
Endothermic
1,2,3 Ionisation energy for sodium
Na (g) > Na+ (g) + e-
Na+ (g) > Na2+ (g) + e-
Na2+ (g) > Na+ (g) + e-
Oxygen ionisation energy
O (g) > O+ (g) + e-
Atoms are singular so not O2
Successive ionisation energy
Measure of energy required to remove each electron in turn
Using graph
Electrons in outer shell = lowest group of crosses
Period number = number of groups
Recognising group number with no graph
Big jump between ionisation energies
Factors that affect ionisation energy
Atomic radius
Electron shielding
Nuclear charge
Atomic radius
Distance from nucleus to outer electron shell
Electron shielding
Amount of shells
Shells lessen electron repulsion
Nuclear charge
Charge of nucleus (protons in nucleus)
Atomic radius across period
Decreases
Atomic radius down a group
Increases
Why does first ionisation energy decrease down a group
Number of shells increases
Shielding increases
Atomic radius increases
Why does first ionisation energy increase across a group
Number of protons increases
Increased nuclear attraction
Atomic radius decreases
Similar shielding
Nuclear attraction
Atomic radius
Nuclear charge
Electron shielding
Boron dip
Bosons outer electron is in a 2p orbital rather than a 2s
2p electron is slightly more distant from the nucleus than the 2s
Also, it is partially shielded by the 2s electrons as well as the inner electrons
Both of these factors offset the effect of the extra proton
Oxygen dip
Despite the extra proton in the oxygen nucleus
Shielding is identical in nitrogen and oxygen and the electron is being removed from an identical orbital
Difference is that in oxygen, the electron being removed is one of the 3px2 pair
Repulsion between the 2 electrons in the same orbital means that the electron is easier to remove than it would otherwise be
Graphite
3BP 1LP
Layers slide easily due to weak forces between layers
Lots of strong covalent bonds so high MP
Delocalised electrons between layers allow graphite to conduct electricity
Layers far apart so low density
Insoluble as covalent bonds too strong strong to break
Diamond
Tetrahedral
Conduct well due to tightly packed rigid arrangement
V high MP due to many strong covalent bonds, v hard
Doesn’t conduct electricity due to no delocalised electrons
Insoluble as covalent bonds too strong
Silicon
Same as diamond
Graphene
1 layer of graphite- 1 atom thick and hexagonal carbon rings
Delocalised free moving electrons make it great conductor of electricity as they can carry a charge
Delocalised electrons strengthen covalent bonds, giving graphine high strength property
1 cell thick lightweight & transparent
Uses in smart phone screens n aircraft shells
Simple molecular
Diatomic, nh3, h2o
Low mbp breaking weak london forces
Giant covalent
Graphite diamond sio2
High m&bp strong covalent bonds
Giant ionic
High mbp strong electrostatic forces of attraction
Metal non metal
Metallic
Metal
High mbp string electrostatic forces of attraction
Giant ionic solubility
As liquid, free ions allow electrical conduction
