Chemistry Chapter 2

Greek for Indivisible

First thought of atom in 5th century BC

Matter cannot be created nor destroyed

All samples of a given compound, regardless where it came from, have the same proportions of their constituent elements.

When two elements form two different compounds, the masses of elemnt B that combine with 1gram of element A can be expressed in small whole number ratios.

Cathode Ray Tube/Cathode Ray/ Electron

Oil drop experiment, determined charge of oil drops.

• Discovered Proton and nucleus
• gold foil experiment

• 1. Nuclues contains 99% of atoms mass
• 2. Atom is mostly empty space
• 3. Atoms have the same number of protons and electrons.

Neutrally charged particles

Define an atom, located in nucleus

Atoms with different numbers of neutrons but same number of protons.

Atomic Mass- Protons

Charged particles/atoms

Negatively charged ions

Positively charged ions

Elements arranged in order of atomic mass have recurring properties

• Group 1A
• Very Reactive

• Group 2A
• Reactive elements

• Group 7A
• Very reactive non metals

• Group 8A
• Do NOT form Ions.
• Mostly unreactive