06a - The Periodic Table

What is the most valuable tool in chemistry that shows patterns in elements?

The periodic table

Which scientist noticed patterns in elements and created the first periodic table?

Dmitri Mendeleev

What did Mendeleev use to organize the 63 known elements?

Flash cards with symbol, atomic mass, and properties

What did Mendeleev do to account for undiscovered elements?

Left open spaces in his table

Which elements’ discovery proved Mendeleev correct?

Germanium, scandium, and gallium

The modern periodic table is arranged by what property?

Atomic number

Who rearranged the lanthanoids and actinoids in the periodic table?

Glenn Seaborg

What does atomic radius measure?

Distance from nucleus center to edge of electron cloud

How does atomic radius change down a group?

Increases

How does atomic radius change across a period?

Decreases

Why does atomic radius increase down a group?

Valence electrons are farther away and shielded by inner electrons

Why does atomic radius decrease across a period?

More nuclear charge pulls electrons closer

What is ionization energy?

Energy required to remove an electron

What is the first ionization energy?

Energy to remove the first electron

What is the second ionization energy?

Energy to remove the second electron

How does ionization energy change up and across a group?

Increases