2.1 Periodicity

• How does atomic radius vary across a period?

  - atomic radius decreases

  - increased nuclear charge as there is an increasing number of protons

  - this pulls teh outer shell of electrons further in towards the nucleus
• How does atomic radius vary down a group?

  Increases down group due to an extra electron shell added for each element down the group
• What is an successive ionisation energy?

  The removal of more than 1 electron from the same atom
• What is the general trend in ionisation energies across a period?

  - Increases

  - increasing number of protons in the nucleus which increases the nuclear attraction

  - shielding is similar and distance from nucleus marginally decreases

  - more energy required to remove an outer electron
• What is the general trend in ionisation energy down a group?

  - decreases

  - atomic radius increases as we go down therefore the outer electrons further from the nucleus so the attractive force is weaker and the energy required to remove an electron decreases
• What is the general trend in shielding down a group and how does this affect ionisation energy?

  Shielding increases as we go down the group because there are more shells between nucleus and outer shell therefore the attractive force is weaker so less energy required to remove an electron