3.2.1 Periodicity Flashcards Preview

A-level Chemistry > 3.2.1 Periodicity > Flashcards

Flashcards in 3.2.1 Periodicity Deck (17):
1

The periodic table is arranged by ____ _____

Atomic number

2

Name the blocks

3

Elements within a period have same number of _____ ___

electron shells

4

Using the periodic table, write the electron configuration for phosphorus

5

Using the periodic table, write the electron configuration for cobalt

6

Atomic Radius _____ across a Period

decreases

7

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

8

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)

9

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

10

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 

11

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

12

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)

13

Why does argon have a very low melting point?

∵ exists as individual atoms = weak van der Waals forces

14

Ionisation energy generally ______ across a period

increases 

15

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

16

Predict the element in Period 3 that has the highest second ionisation energy. Give a reason for your answer. (2)

  • Sodium / Na
  • Electron (removed) from the 2nd shell / 2p (orbital)

17

Explain why the ionisation energy of every element is endothermic (1)

Energy needed to overcome attraction between nucleus and electron