Periodic trends are the predictable patterns in element properties across the periodic table, especially atomic radius, ionization energy, electronegativity, and metallic character.
As you move across or down the periodic table, element behavior changes in regular, trackable ways.
Showing a random 20 of 50 problems.
Example 1
challenge
Explain why fluorine has a smaller atomic radius than oxygen, and why both are smaller than nitrogen.
Example 2
challenge
Sodium's first ionization energy is 496 kJ/mol but its SECOND is 4562 kJ/mol. Explain the huge jump.
Example 3
easy
Do atomic radius and ionization energy trend in the same or opposite directions?
Example 4
medium
Rank by increasing atomic radius: O, S, Se.
Example 5
medium
Rank by increasing first ionization energy: B, C, N.
Example 6
medium
Two elements are isoelectronic: Na+ and Mg2+ (both 10 electrons). Which has the smaller radius?
Example 7
easy
How does atomic radius change across a period from left to right?
Example 8
easy
Which element has higher electronegativity: O or S?
Example 9
challenge
Using periodic trends only, predict whether CaF2 or CaI2 has the higher melting point.
Example 10
hard
Element Q has successive IEs (kJ/mol): 738, 1451, 7733, 10540. Which group is Q in?
Example 11
medium
Atom X has IE1 = 580 kJ/mol and IE2 = 1820 kJ/mol; atom Y has IE1 = 740 and IE2 = 1450 kJ/mol. Which is more likely a group 1 element?
Example 12
easy
Which has higher ionization energy: Na or Ar (same period)?
Example 13
medium
Predict which atom is more electronegative: Si or Cl.
Example 14
medium
The element with the highest first ionization energy is ____.
Example 15
hard
Explain the anomaly: O has lower IE1 than N despite N having fewer protons.
Example 16
medium
Which is larger: Fe2+ or Fe3+?
Example 17
medium
Rank by decreasing atomic radius: Na, Mg, Al, Si.
Example 18
hard
Using trends only, predict whether the bond in MgO is more or less ionic than the bond in MgS.
Example 19
medium
Which is larger: a neutral Cl atom or its anion Cl−?