Periodic Table

Who created the first widely published periodic table?

Dmitri Mendeleev, a Russian chemist, in 1869.

How did Mendeleev organize the elements in his table?

By increasing atomic mass and grouping similar properties.

Why did Mendeleev leave blank spaces in his table?

For undiscovered elements, predicting their masses and properties.

How were Mendeleev’s predictions proven correct?

Later discoveries matched his predicted element properties.

What was Mendeleev’s key innovation?

Accurately predicting unknown elements’ characteristics from gaps.

How is the modern periodic table arranged?

By increasing atomic number, not atomic mass.

What does the Periodic Law state?

When arranged by atomic number, element properties repeat periodically.

What does a group number represent?

The number of valence electrons (skipping the d-block).

What does a period number represent?

The number of occupied energy levels in an atom.

What are valence electrons?

Outermost electrons involved in chemical bonding.

What are elements in Group 1 called?

Alkali metals.

How reactive are alkali metals, and what’s the trend?

Highly reactive; reactivity increases down the column.

What are elements in Group 2 called?

Alkaline earth metals.

How reactive are alkaline earth metals compared to alkali metals?

Reactive but less so; reactivity increases down the group.

What are elements in Group 17 called?

Halogens.

How does halogen reactivity change within the group?

Increases upward the column.

What are elements in Group 18 called?

Noble gases.

Why are noble gases least reactive?

They have full valence shells and rarely form ions.

Which groups are the transition metals?

Groups 3–12.

What are elements 57–71 called?

The Lanthanide Series.

What are elements 89–103 called?

The Actinide Series.

How has the periodic table evolved over time?

Through discovery of new elements and changing knowledge.

What happened to old element names and symbols?

Many were replaced or modernized.

What was the key organizational change from early tables?

Shift from atomic mass to atomic number arrangement.

How are modern periodic table elements arranged?

By increasing atomic number in rows and columns.

What do horizontal rows on the table represent?

Periods.

What do vertical columns represent?

Groups or families.

What do elements in the same group share?

Similar chemical properties.

What’s the purpose of the table’s color coding?

To distinguish element categories and groups.

What does yellow represent in color coding?

Specific element categories.

What does blue represent in color coding?

Different element groups.

What does pink represent in color coding?

Additional classifications.

Rows (vertical) =

Groups (group 1,2,3,4-18)

Columns (horizontal) =

Periods (<—>)