can somebody help with parts c and d

Answer:
13. Na 14. Ne. 15. U. 16. Ca. 17. C. l 18. O. 19. Cl. 20. Si 21. U 22. N.
23. Na 24. Ne. 25. U 26. Sc. 27. N 28. O 29. Cl 30. Si 31. U 32. N.
Explanation:
The general trend as you go to the right in any one period is for the size to decrease.
The general trend is that the size increases as you go down a Group.
The general trend as you go from the bottom left to the top right is a decrease in size.
Ionization energy increases as we move to the right in a period.
It decreases as we move down a group.
Going from the bottom left to top right - the ionization increases.