The Periodic Table: Atomic Radius, Ionization Energy, and Electronegativity

Who created the version of the periodic table that became widely accepted and why?

Dmitri Mendeleev, because his table correlated data well and predicted undiscovered elements.

What are the rows and columns of the periodic table called?

Rows are called periods; columns are called groups.

Why do elements in the same group behave similarly?

Because they have the same number of valence electrons.

What happens to atomic radius as you move down a group in the periodic table?

It increases because new electron shells are added.

What happens to atomic radius as you move from left to right across a period?

It decreases because the nucleus has more protons, pulling electrons closer.

How does gaining or losing electrons affect ionic radius?

Gaining electrons increases radius; losing electrons decreases radius.

What is ionization energy?

The energy required to remove an electron from an atom.

How does ionization energy change across the periodic table?

It increases from left to right and decreases from top to bottom.

Why is francium easy to ionize?

It has a large atomic radius and only one valence electron far from the nucleus.

Why does helium have a high ionization energy?

Its electrons are close to the nucleus and it has a full outer shell.

What causes sudden jumps in successive ionization energies?

Removing electrons from a full, stable shell (like a noble gas configuration).

Why is oxygen’s ionization energy lower than nitrogen’s, despite having more protons?

Due to orbital symmetry; nitrogen’s half

What is electron affinity?

The amount of energy released when an atom gains an electron.

Which element has the highest electron affinity and why?

Fluorine, because gaining one electron gives it a full outer shell.

What is electronegativity?

An atom's ability to attract and hold onto electrons.

How does electronegativity change across the periodic table?

It increases from left to right and from bottom to top (excluding noble gases).

What are the four major periodic trends to remember?

Atomic radius (↓←), ionization energy (↑→), electron affinity (↑→), electronegativity (↑→).