Fundamental Scientific Method and Atomic Structure Concepts

Seven Primary Dimensions

There are 7 primary dimensions:

• Length (meter, m)
• Mass (kilogram, kg)
• Time (second, s)
• Temperature (kelvin, K)
• Electrical Current (ampere, A)
• Light Intensity (candela, cd)
• Amount of Substance (mole, mol)

Note: 1 liter (l) equals 1 cubic decimeter (dm³).

The Scientific Method

A) Observation

Please note: Asking questions begins by observing phenomena perceived through our consciousness. Observation implies curiosity.

B) Formulation of Hypotheses

Hypotheses are possible answers to the questions raised during observation.

C) Experimentation

Experimentation checks whether the assumptions made are true or false. In this stage, perform the following:

1. Design and assembly of experiments.
2. Data collection.
3. Measurement of quantities.

D) Analysis of Results

When an experiment is finished, there will generally be a series of data or measurements to analyze to determine if the hypothesis is true or false. To do this, scientists use three methods:

1. Elaboration of tables of values.
2. Graphing.
3. Derivation of mathematical equations.

E) Formulation of Laws and Theories

When a hypothesis is proven true and can explain a large number of natural events, it is called a law. The set of laws that explain a phenomenon is known as a theory.

Early Concepts of Electricity and Matter

Faraday's Contributions

Faraday studied the passage of electricity through salt solutions. Scientists proposed that matter must contain particles with electrical properties. They proposed that matter contains two types of electrical charge: positive and negative. To measure the amount of electricity used, the coulomb (C) is employed. Positive atoms are called positive ions or cations; negative atoms are called negative ions or anions.

Thomson's Atomic Model

The first model was due to Thomson, implying the existence of a sphere of positive electricity. At that time, the proton had not yet been discovered. However, experiments with radioactivity showed that Thomson's atomic model did not conform to reality.

Rutherford's Model and Experiment

(The most important experiment is due to Rutherford, who used alpha ($\alpha$) radiation. Alpha particles are much smaller and have a positive charge. These particles were directed against a thin gold foil, and the resulting deflection was observed on a screen placed behind the foil.)

Rutherford's Conclusions

Rutherford developed a series of conclusions:

1. Matter is virtually empty because most particles passed through without deviation.
2. The positive charges occupy a very small space inside the atom. This core space is called the nucleus; it is the positive part of the atom and contains most of its mass.
3. Neutral particles must also exist in the nucleus to avoid repulsion between positive particles.
4. Electrons move around the nucleus so they do not fall into it. This area is called the cortex.

Definition of an Atom

An atom is a space where electrons can move and orbit, whose nucleus contains protons and neutrons (implied by the need for neutral particles).