Q.Justify the position of lanthanides and actinides in the periodic table.

Step 1. State their formal position: by strict electron-filling order, the lanthanides sit at group 3, period 6 (directly following La), and the actinides sit at group 3, period 7 (directly following Ac).

Step 2. Explain why they are NOT shown inline there: after La (or Ac), the next electrons added fill the INNER 4f (or 5f) sub-shell, not an outer valence orbital -- so these fourteen elements share the distinguishing feature of an inner-shell-filling pattern that leaves their valence-shell chemistry very similar element to element.

Step 3. Because of this shared inner-filling pattern, all fourteen lanthanides (and, similarly, all fourteen actinides) show closely similar chemical properties to one another, and nearly all share the same common oxidation state, +3. …

State the lanthanides'/actinides' true electron-filling position, then justify their detached placement via the three chapter-given reasons: inner-shell filling, …

• Stating only 'they don't fit' without explaining WHY inline placement would be structurally disr …