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Here are the answers to the question in CP Questions for Periodic Trends Coulombic Force, Atomic Radii and Electronegativity.
1. Decrease.
Reason: As you go down a Group, the valence electrons are in higher Energy level (n), causing the electron to be farther from the nucleus so the CF decreases (less pull of nucleus to the valence electrons).
2. Top right.
3. Atomic size decreases as you go across a Period.
Reason: Since the nuclear charge is increasing causing a greater pull to valence electrons (greater CF) the valence electron are closer (since they are on the outside of atom, they determine size of atom).
4. Top Right
5. Nucleus of atom has great "pull" (i.e. Coulombic force, CF) for valence electrons. In other words,
High EN value elements has high CF
6. EN increases as go across
Reason: since the nuclear charge is increasing causing the nucleus to have a greater pull (CF) to the nucleus.
7. Top right
8. Cs, Ca, Ni, C, O
9. Rb, Mg, P, Cl
10. F, C, Al, K