The Periodic Table

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Who was Dobereiner?

A scientist who developed the concept of triads

What is a triad?

A set of three elements with similar properties

When did Dobereiner live?

1780-1849

How did Dobereiner organize the elements?

He organized them into triads by atomic mass

What law did Dobereiner come up with?

The law of triads

What pattern did Dobereiner notice?

He noticed the middle element had the average mass of the other two elements in the triad

Who was Newlands and how did he organize the elements?

A chemist that organized elements by atomic weight and found a pattern

What law did Newlands come up with?

The law of octaves (eight)

What pattern did Newlands notice?

Every eight element in his version of the periodic table had similar properties

When did Newlands come up with his theory?

1864

Who was Mendeleev?

The father of the periodic table

How did Mendeleev organize the elements?

Atomic mass and properties of the elements

Why did Mendeleev leave gaps in his periodic table?

He predicted undiscovered elements

How did Mendeleev predict elements that haven't been discovered yet?

Based on the elements near it and by comparing it to nearby elements

How is the modern periodic table arranged?

By atomic number

What is a column called on the periodic table?

A group

What is a row called on the periodic table?

A period

What are group 1 elements?

Alkali metals

What are group 2 elements?

Alkali earth metals

What are group 7 elements?

Halogens

What are group 0 elements?

Noble gases

What do elements in the same group have in common?

They have the same number of valence electrons and they have similar chemical and physical properties

What is a valence electron?

An electron in the outer shell

What do elements in the same period have in common?

They have the same number of outer shells

Why does aragon have a higher atomic mass than silver?

Because it has more neutrons

What are transition metals?

Metals in groups 3-12