Periodicity
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What is position of elements on periodic table linked to?
Chemical and physical properties
How is atomic number used in arrangement of the periodic table?
Increases from left to right across periodic table, each successive element has one extra proton
What is similar between each element in the same group?
Same number of outer shell electrons Similar chemical properties
What does the number of the period indicate?
Number of highest energy electron shell in an element’s atom
Define periodicity
Repeating trend in properties of elements
What is ionisation energy a measure of ?
How easily an atom loses an electron to form positive ions
Define first ionisation energy
The amount of energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
What 3 factors affect ionisation energy?
Atomic Radius Nuclear Charge Electron Shielding
Do successive ionisation energies decrease or increase?
Increase because the electron is experiencing a greater attraction to the nucleus
What do large jumps in ionisation energy show?
Changes in shells
What are the 2 key patterns in ionisation energy in first 20 elements?
A general increase in first ionisation energy across a period A sharp decrease in first ionisation between end of one period and start of the next
Explain trend in ionisation energy down a group
Decreases Atomic Radius increases More shells so shielding increases Proton number increases Nuclear attraction decreases Requires less energy to remove electron
Explain trend in ionisation energy across a period
Nuclear Charge increases Similar shielding Small atomic radius First ionisation energy increases as more energy required due to greater attraction
Why is there a fall in ionisation energy between Be and B?
B has outer electrons in 2p which has higher energy level than the 2s sub shell and so is easier to remove because it is solitary and requires less energy, therefore first ionisation energy is less.
Why is there a fall between N and O?
O marks the start of pairing of electrons, the paired electrons in the 2p orbital cause repulsion which means that it is easier to remove an electron. Lowers first ionisation energy.
Which elements are semi-metals?
Geranium and Silicon
Define metallic bonding
Strong electrostatic attraction between cations and a sea of delocalised electrons
What are the 3 common properties of most metals?
Strong metallic bonds High electrical conductivity High melting and boiling points
Why can metals conduct electricity?
Delocalised electrons can move through the structure carrying charge
Explain trend in melting and boiling points of metallic lattices
Strong electrostatic force of attraction between the positively charged atoms and delocalised electrons requires a lot of energy to overcome
Are metallic lattices soluble?
No, there is little interaction
Describe shape and bond angle of diamond
109.5 Tetrahedral
What are the melting and boiling points of giant covalent lattices like?
High Requires a large proportion of energy to overcome and break strong covalent bonds
Are giant covalent lattices soluble?
No, the covalent bonds are too strong to be broken by interaction with solvents