Unit A: Energy And Matter In Chemical Change | Outcome 1 | L 1 - L2

Question 1

What is an atom?

Answer 1

The smallest unit of any element

“Atomos” = “uncuttable”

Question 2

In what order were the model of atoms created?

Oldest to newest

Answer 2

Billiard Ball (Dalton), Plum Pudding (JJ Thompson), Planetary Model (Rutherford) and Bohr Model (Bohr)

Question 3

What was the main idea of the Billiard Ball?

Answer 3

• All matter is made of atoms, which are small spheres
• Atoms are indivisible, indestructible and cannot be created
• Atoms of a given element are the same and atoms can combine to form new substances

Question 3

What did Aristole believe?

(400 B.C.E)

Answer 3

• All things were made up of 4 elements: earth, fire, wind and water

This was a “lucky guess” as Aristole had no proof. Yet this theory caused more correct ideas from Philosophers such as Democritus to be ignored.

Question 3

How did J.J Thompson discover electrons?

Joeseph John Thompson (1808)

Answer 3

• After experiemnting and observing cathode rays rays in gas discharge tubes

Question 4

What was the main idea of the Plum Pudding Model?

Answer 4

• Atoms are a positively charged sphere with negative pieces (electrons) embedded in it

…making it a neutral atom

Question 5

What did Democritus believe?

(400 B.C.E)

Answer 5

• Believed that matter could not be divided into smaller and smaller pieces forever, eventually the smallest possible piece
  would be reached

He named the smallest piece of matter “atomos, meaning “not to be cut”

Question 6

What was the main idea of the Planetary Model?

Answer 6

• All the atom’s positive charge and most
  of its mass is concentrated in the center
  (nucleus)
• Electrons orbit around the nucleus and
  have lots of volume but very little mass

Question 7

What was the main idea of the Bohr Model?

Answer 7

• Electrons surround the nucleus in specific
  energy levels
• They cannot exist in between levels

Question 8

What is the symbol for protons?

Answer 8

p⁺

Question 9

What is the symbol for neutrons?

Answer 9

n^-

Question 10

What is the symbol for electrons?

Answer 10

e^-

Question 11

What is an atomic number

Answer 11

• The number of protons in the nucleus
• Identifies the element

number of protons = number of electrons for a neutral atom

Question 12

What is the atomic mass

Answer 12

• atomic mass = number of protons + number of neutrons
• Can be rearranged to determine number of neutrons

- neutrons = mass – protons

Question 13

What are isotopes?

Answer 13

• Atoms of the same element that have the same
  number of protons but different numbers of neutrons

• The mass found on the periodic table is the average of
  the various isotopes of an element