Chem

Element

A substance which can NOT be decomposed

Compound

A substance that can be decomposed

Homogenous

Same composition throughout a sample.

Heterogenous

Different composition throughout a sample

Physical Properties

Color, ordor, density melting point, boiling point, and hardness

Chemical Properties

Flammability, toxicity, acidity, reactivity with water, reactivity with oxygen, and heat of combustion

Physical Changes

Changes of state, temperature, and volume

Element

A substance which can NOT be decomposed

Compound

A substance that can be decomposed

Homogenous

Same composition throughout a sample.

Heterogenous

Different composition throughout a sample

Chemical Properties

Flammability, toxicity, acidity, reactivity with water, reactivity with oxygen, and heat of combustion

Physical Changes

Melting, freezing, boiling, bending, cutting, and dissolving

Chemical Changes

Combustion, oxidation, decomposition, burning wood, cooking an egg, digesting food

Precision

How close a number is to another

Accuracy

How close numbers are to true value

Demoentus

Matter is a thing made of atoms

• substances were made of different atoms

Dalton

=Atomic Theory

• Made the 5 Postulates

J.J Thomson

• Cathode Ray Experiment

• Discovered Electrons and It’s charge

• First Model of an Atom “Plum-Pudding Model”

E. Rutherford

• Gold Foil Experiment

• Discovered Nucleus

• Protons are Positive

• Most atom’s mass is from the nucleus

Millikan

• Oil Drop Experiment

• Discovered the Mass-to-change ratio of an electron

• Calculated the mass of an electron

• Electron=-1.602×10^-19C

James Chadwick

• Radioactive Experiment

• Discovered Neutron

Niels Bohr

Created the Bohr Model/ Planetary Model

• Used Calculations to construct model

• Only accurate how close an electron is to the nucleus

Max Plank

Created Quantum Mechanics

ORBITALS

• Sphere

• Dumbbell

• Clover

• Flower

Gold Foil Experiment Results

• The volume occupied by an atom most consist of a large amount of empty space

• A small relatively heavy, positively charged body, the nucleus must be at the center of each atom

• the proton was discovered as the positively charged

Postulates of John Dalton’s Atomic Theory

1. All matter is composed of extremely small, indivisible particles called atoms.

   • Status: Incorrect (Modified)

   • Why: Atoms are not indivisible. The experiments of Thomson, Rutherford, and Chadwick proved that atoms are composed of smaller subatomic particles: electrons, protons, and neutrons. Additionally, atoms can be split or transformed into other atoms through nuclear reactions.

2. All atoms of a given element are identical in size, mass, and other properties.

   • Status: Incorrect

   • Why: The discovery of isotopes showed that atoms of the same element can have different numbers of neutrons and therefore different atomic masses (e.g., carbon-12 and carbon-14).

3. Atoms of different elements differ in size, mass, and chemical properties.

   • Status: Mostly Correct

   • Why: While atoms of different elements generally have different masses and chemical properties, isobars exist (atoms of different elements that have the same total mass number, such as 40Ar40Ar and 40Ca40Ca).

4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds.

   • Status: Correct

   • Why: This forms the basis of the Law of Definite Proportions and the Law of Multiple Proportions in chemical reactions.

5. In chemical reactions, atoms are combined, separated, or rearranged, but are never created or destroyed.

   • Status: Correct for ordinary chemical reactions.

   • Why: This reflects the Law of Conservation of Mass. However, in high-energy nuclear reactions, mass can be converted into energy.