Periodicy Flashcards
How are elements arranged in the periodic table?
By increasing atomic number
What do elements in the same period have in common?
Highest energy electron in the same shell
What do elements in the same group have in common?
Same number of electrons in the highest energy shell
How and why did Mendeleev arrange the elements?
By atomic weight
Nothing was known about sub atomic particles
Define periodicy
Trends in properties of elements in the periodic table
Define ionisation energy
The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions
What factors affect ionisation energy?
Atomic radius
Nuclear charge
Shielding
How does shielding affect ionisation energy?
Inner shell electrons repel outer shell electrons making them easier to remove
How does atomic radius affect ionisation energy?
Larger atomic radius means electrons are further away from nucleus
Less attraction
Easier to remove
How does nuclear charge affect ionisation energy?
Larger means larger attraction
Electrostatic force of attraction stronger means more energy needed to break
How do successive ionisation energies provide evidence for atomic structure?
Large increase suggests electrons are closer to nucleus.
Evidence for shells
Number of electrons removed before increase indicates electrons in outer shell
Does ionisation energy increase or decrease down a group?
Why?
Decreases
Larger atomic radius (more shells)
More shielding (more shells)
Larger nuclear charge (outweighed by other factors )
Does ionisation energy increase or decrease across a period?
Why?
Increases
Nuclear charge increases
Atomic radius decreases
Shielding is similar so no effect
Why is there an unexpected decrease between ionisation energies between group 2+3 and 5+6?
2+3 = P subshell begins to fill (further from nucleus means easier to remove)
5+6= electrons begin to pair so feel repulsion (easier to remove)
What are semi metal?
What is another name for them?
Elements either side of the metal non-metal divide
Metalloid
What is the structure of metals and giant covalent molecules know as?
Giant lattice
Why are metals not soluble?
They react instead
Partial charges not strong enough to break strong metallic bonds
What is the shape of diamond and silicone?
Tetrahedral
What is the difference between graphene and graphite ?
Graphite = layers of graphene
What is the structure of graphite ?
Giant planar structure
Are giant covalent structures soluble?
Why?
Not soluble
Partial charges can’t break strong covalent bonds
Why is there a general increase in melting points across the metals in the same period?
Higher charge on ion
More delocalised electrons
More stronger forces to overcome
Where and why do the melting points of elements peak across period 3?
At silicone
Silicone is a giant covalent structure
Phosphorus is a simple molecule
Covalent VS weak London forces
Order in decreasing strength giant covalent , simple molecules and ionic (metallic) bonding .
Covalent ionic simple
Why does silicone have a higher melting point than phosphorus ?
Silicone = S8
Phosphorus = P4
Larger molecule = more electrons = stronger induced dipoles = stronger London forces
