UNDERSTANDING CONCEPTS-Fill in the Blanks: Periodic Trends: Write either INCREASE or DECREASE or VARIABLE:
17.lon size = Atom → Cation
18. Atomic radius (size) = Down a group
19. Electronegativity = Across a period left
20. Ionization energy = Down a group
Atom Anion
Across a period right
Up a group
Across a period left

17 decrease

18 increase

19 increase

20 decrease

Explanation:

lithosphere and asthenosphere

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."