Atomic Theory and Early Atomic Models

Flashcards covering Dalton, Thomson, Rutherford, and Bohr concepts from the notes.

What is the name of John Dalton’s theory?

The atomic theory of matter.

What are elements made of?

Atoms.

According to Dalton's atomic theory, how do atoms of different elements compare to each other?

They are different.

What are compounds made of?

Atoms of different elements combining in definite whole-number ratios.

The ratio of atoms in HCl is:

1:1

The ratio of atoms in H2O is:

2:1

What did J.J. Thompson discover?

The electron.

What is the charge of an electron?

Negative.

What are cathode rays made of?

Electrons (negatively charged particles).

Why do electrons move from the negative end of the tube to the positive end?

Because electrons are negatively charged and are attracted toward the positively charged end (the positive electrode).

What was Thompson working with when he discovered the cathode rays?

Gas discharge tubes.

What is the charge of an alpha particle?

Positive.

Why is Rutherford’s experiment called the gold foil experiment?

Because he used a thin sheet of gold foil to test how alpha particles pass through.

How did he know that an atom was mostly empty space?

Most alpha particles passed straight through the foil.

What happened to the alpha particles as they hit the gold foil?

Most passed through, some were deflected, and a few bounced back.

How did he know that the nucleus was positively charged?

Alpha particles were repelled by the positively charged nucleus, causing deflections or backscatter.

Why could Bohr’s model be called a planetary model of the atom?

Because electrons orbit the nucleus like planets around the sun.

How do electrons in the same atom differ?

They occupy different energy levels (energy states) within the atom.

How many electrons can the fourth energy level hold?

32.

Would an electron have to absorb or release energy to jump from the second energy level to the third energy level?

Absorb energy.

And for an electron to fall from the third energy level to the second energy level?

Release energy.