Periodicity
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What will all the elements within a period have the same number of?
Electron shells (If you don’t worry about s and p sub-shells) E.g. All period 2 gave 2 electron shells
All elements within a group will have the same number of?
Electrons in their outer shell so have similar properties
What does the group number tell you?
The number of electrons in the outer shell, group 4 elements have 4 electrons and so on. The exception is group 0 which have full electron shells that’s two electrons in helium, 8 electrons for all the others
How can the periodic table be split?
Into an s block, d block, p block and f block. Doing this shows which sub-shell all the electrons go into.
What can you do you have labelled the blocks and numbered them?
Read off electronic structure of any element. Just start at the top and work your way across and down until you get the element
What happens as the number of protons increases?
The positive charge of nucleus increases meaning electrons are pulled closer to the nucleus making the atomic radius smaller.
What does the extra electrons gained across a period do?
Get added to the outer energy level so they don’t provide any extra shielding effect. Shielding is mainly provided by electrons in the inner shells
How is the periodic table arranged?
Periods and groups by atomic (proton) number
What will all the elements within a period have the same number of?
Electron shells (If you don’t worry about s and p sub-shells) E.g. All period 2 gave 2 electron shells
All elements within a group will have the same number of?
Electrons in their outer shell so have similar properties
What does the group number tell you?
The number of electrons in the outer shell, group 4 elements have 4 electrons and so on. The exception is group 0 which have full electron shells that’s two electrons in helium, 8 electrons for all the others
How can the periodic table be split?
Into an s block, d block, p block and f block. Doing this shows which sub-shell all the electrons go into.
What can you do you have labelled the blocks and numbered them?
Read off electronic structure of any element. Just start at the top and work your way across and down until you get the element
What happens as the number of protons increases?
The positive charge of nucleus increases meaning electrons are pulled closer to the nucleus making the atomic radius smaller.
What does the extra electrons gained across a period do?
Get added to the outer energy level so they don’t provide any extra shielding effect. Shielding is mainly provided by electrons in the inner shells
How is the periodic table arranged?
Periods and groups by atomic (proton) number
What do melting points do across a period?
Vary because they depend on the structure and the bonding within them.
What are sodium, magnesium and aluminium?
Period 3 metals
What happens to sodium to aluminium melting point and boiling points?
Increase across the period because the metal- metal bonds get stronger. The bond get stronger because the metal ions have an increasing positive charge, an increasing number of delocalised electrons and decreasing radius
Describe why silicon has a high melting point?
Macromolecular with a tetrahedral structure- string covalent bonds link all its atoms together. A lot of energy is needed to break these bonds so silicon has a high melting point
Explain why phosphorus (P4), sulfur (S8) and chlorine (Cl2) have low melting point?
All molecular substances. Their melting points depend upon the strength of van der Waals forces which are weak and easily overcome
What do more atoms in a molecule mean for van der Waal forces?
They are stronger van der Waals forces and sulfur is the bigger molecule so it’s got a higher melting point than phosphorus or chlorine
Why does argon have a very low melting point?
It exists as individual atoms (monatomic resulting in very weak van der Waals forces.
What do ionisation energies generally do across a period and why?
Increase because of the increasing attraction between outer shell electrons and the nucleus due to the number of protons increasing. (Few blips in this trend however)