3.2.1 Periodicity Flashcards
The periodic table is arranged by ____ _____
Atomic number
Name the blocks
Elements within a period have same number of _____ ___
electron shells
Using the periodic table, write the electron configuration for phosphorus
Using the periodic table, write the electron configuration for cobalt
Atomic Radius _____ across a Period
decreases
Why does atomic radius decreases across a period?
- As number of proton increases, positive charge of nucleus increases
- Increased attraction between nucleus and electrons
- Similar shielding in each period
- As electrons added to same outer shell
Why don’t the extra electrons that element gains across period provide extra shielding?
- Extra electrons are added to outer energy level
- (Shielding is mainly provided by electrons in inner shells)
As you go across period 3, from sodium to magnesium to aluminium, why does melting and boiling points increase?
- ∵ metal-metal bonds get stronger
- Get stronger ∵ metal ions have increasing positive charge = increasing number of delocalised electrons and decreasing radius
Why does silicon have such a high melting point?
- Silicon is macromolecular (tetrahedral structure) = many strong covalent bonds
- Lot of energy needed to break these bonds
Why does phosphorus, sulfur and chlorine have low melting points?
- They’re molecular substances so melting points depend upon strength of van der Waals forces between molecules
- Van der Waals forces are weak and easily overcome
Why does sulfur have a higher melting point than phosphorus or chlorine? (2)
- Sulfur is the biggest molecule (largest Mr)
- Stronger van der Waals forces between molecules (they’re stronger with larger Mr)
Why does argon have a very low melting point?
∵ exists as individual atoms = weak van der Waals forces
Ionisation energy generally ______ across a period
increases
Why does ionisation energy generally increases across a period (4)
- As number of proton increases, positive charge of nucleus increases
- Increased attraction between nucleus and electrons
- Similar shielding in each period
- As electrons added to same outer shell
- More energy needed to remove electron