History Of The Atom

Question 1

What is an element?

Answer 1

It is a substance that cannot be broken down further into simpler substances.

Question 2

What is an atom?

Answer 2

An atom is the smallest unit of an element, having the properties of that element

Question 3

What is a compound?

Answer 3

A compound is a substance formed when two or more chemical elements are chemically bonded together.

Question 4

What is a molecule?

Answer 4

A molecule is a particle made up of two or more atoms that are chemically bonded together.

Question 5

John Dalton-Model and Year

Answer 5

1803

Solid Sphere Model

Question 6

What was Dalton right about?

Answer 6

-Recognized atoms of a particular element differ from other elements

Question 7

What was Dalton wrong about?

Answer 7

Atoms aren’t indivisible-they’re composed from subatomic particles

Question 8

J.J. Thomson-Model and Year

Answer 8

Plum Pudding Model

1904

Question 9

What did Thomson’s theory suggest?

Answer 9

• He discovered electrons

- His model shows the atom as composed of electrons scattered throughout a spherical cloud of positive charge.

Question 10

Rutherford-Model and Year

Answer 10

Nuclear Model

1911

Question 11

What was Thomson right about?

Answer 11

Recognized electrons as components of atoms

Question 12

What was Thomson wrong about?

Answer 12

No, nucleus; didn’t explain later experimental observation

Question 13

What was Rutherford’s experiment?

Answer 13

He fired positively charged alpha particles at a thin sheet of gold foil. Most passed through with little deflection but some deflected at large angles.

Question 14

What was Rutherford wrong about?

Answer 14

Did not explain why electrons remain in orbit around the nucleus

Question 15

What was Rutherford right about?

Answer 15

Realized positive charge was localized in the nucleus of an atom.

Question 16

Bohr-Model and Year

Answer 16

Planetary Model

1913

Question 17

What did Bohr modify?

Answer 17

He modified Rutherford’s model of the atom by stating that electrons moved around the nucleus in orbits of fixed sixes and energies. Electron energy was quantized.

Question 18

What was Bohr right about?

Answer 18

Proposed stable electron orbits

Question 19

What was Bohr wrong about?

Answer 19

Moving electrons should emit energy and collapse into the nucleus.

Question 20

Erwin- Model and Year

Answer 20

Quantum Model

1926

Question 21

What did Schrödinger suggest?

Answer 21

Erwin stated that electrons move around in set paths around the nucleus but rather in waves. Because it is impossible to know the exact location of an electron instead we have clouds of probability called orbitals.

Question 22

What was Erwin right about?(2)

Answer 22

• Showed electrons don’t move around the nucleus in orbits, but in clouds where the position is uncertain.
• Still widely accepted as the most accurate model of an atom.

Question 23

Name 4 important things regarding Dalton’s theory.

Answer 23

• All matter is made up of tiny indivisible particles called atoms
• All atoms of a given element are identical in mass and properties
• Atoms of different elements combine in simple whole number ratios to form chemical compounds
• In chemical reactions, atoms are combined, separated or rearranged