Atomic Theory

Question 1

Democritus

Answer 1

• Greek philosopher who discovered “atmos” an indestructible particle that cannot be divided
• Believed all matter was made of “atmos” and that they were uniform, solid, and indestructible

Question 2

John Dalton

Answer 2

• An English chemist who created the three principles of atomic theory:
  1. Elements are made of indivisible particles (atoms)
  2. All atoms of the same element are identical
  3. Atoms can neither be created nor destroyed

Question 3

J. J. Thomson

Answer 3

• An English physicist who conducted the cathode ray tube experiments
• Showed that all atoms contained negatively charged particles called electrons

Question 4

Ernest Rutherford

Answer 4

• A Physicist from New Zealand who conducted the gold foil experiment
• Hit a piece of gold foil with alpha particles which had a positive charge
• Most went through but some bounced off the gold foil, showing most of the atom is empty space but there’s something hard within each atom (nucleus)

Question 5

James Chadwick

Answer 5

• An English physicist who used a neutron chamber to test atoms
• Discovered that some atoms are heavier/lighter even if they are the same element
• Discovered atoms don’t just contain protons and electrons but also neutrons

Question 6

Niels Bohr

Answer 6

• A Danish physicist who proposed that atoms have electron shells
• Showed a central nucleus with protons and neutrons with circular electron shells around the nucleus

Question 7

Electromagnetic radiations from least energy to most energy

Answer 7

• Radio
• Microwave
• Infrared
• Visible
• Ultraviolet
• X-ray
• Gamma Ray

Question 8

Difference between an ion and an atom

Answer 8

• Atoms are neutral and contain the same number of protons and electrons
• Ions are particles with a different number of protons and electrons because of an electrical charge adding or removing atoms

Question 9

Valence Electrons

Answer 9

• Electrons in the outermost shell of an atom

Question 10

Electrons in the first four energy levels of an electron

Answer 10

1st: 2 Electrons
2nd: 8 Electrons
3rd: 8 Electrons
4th: 18 Electrons

Question 11

Wave-particle duality of light and electrons

Answer 11

• Electrons possess both the properties of waves and particles
• Light was first seen as acting like a wave, but was later found to have particle-like aspects

Question 12

Atomic Orbitals

Answer 12

• A three-dimensional description of the most likely locations for electrons around atoms (dumbbell-like)

Question 13

Principal Quantum Number

Answer 13

• A quantum number assigned to electrons to describe the electron’s state
• Describes the size of the orbital