Atomic Models and Chemical Compounds: A Comprehensive Study
Atomic Models and Chemical Compounds
Thomson’s Atomic Model
Imagine the atom as a lump of positively charged matter with negatively charged electrons embedded within it, like a watermelon.
Rutherford’s Gold Foil Experiment
Rutherford decided to bombard atoms in a very thin gold foil with projectiles. He used newly discovered particles, much smaller than atoms but very heavy, with a mass four times greater than that of a hydrogen atom and a charge twice that of an electron, but positive. These particles were fired spontaneously at high speeds.
Results of the Experiment
- Most of the particles crossed the gold foil undeflected.
- Some of these particles suffered deviations.
- Rarely, some particles bounced back.
Interpretation of the Results
- Most of the particles did not deviate because matter is mostly empty space.
- Some particles were deflected when passing near very heavy and positively charged particles.
- Some particles bounced back when colliding with the nucleus.
Rutherford’s Atomic Model
Rutherford’s atomic model consists of an almost empty sphere, formed by two parts:
- The Shell: Consisting of all the electrons in an atom.
- The Nucleus: A very small region containing the entire positive charge and nearly all the mass of the atom.
Fundamental Atomic Particles
Protons and neutrons are found in the nucleus, and electrons in the shell.
Atomic Number and Mass Number
The atomic number (Z) is the number of protons that an atom contains. The mass number (A) is the sum of protons and neutrons in the nucleus. The number of neutrons is calculated as: n = A – Z.
Ions
Ions are atoms that have a net charge due to a deficiency or excess of electrons.
Relative Atomic Mass
The atomic mass unit is taken as the mass of a hydrogen atom, denoted as msa(H).
Isotopes and Chemical Elements
Isotopes are atoms of the same element that have different numbers of neutrons. Chemical elements are substances formed by identical atoms.
Classification of Elements
Elements are classified as metals and non-metals. Metals, except for gold (Au) and copper (Cu), are grayish and have a metallic luster. They are good conductors of heat and electricity and have high melting and boiling points. They can be spun and laminated. Non-metals are bad conductors and have low density.
Physical and Chemical Changes
Physical changes are those that alter some properties of a substance without changing its composition. Chemical changes transform one substance into another.
Chemical Reactions
A chemical reaction is the process by which chemical changes occur.
Chemical Formulas
Formulas are the representation of chemical compounds using symbols. The molecular formula of compounds formed by molecules includes the symbols of the corresponding elements and a subscript. The empirical formula of aggregates forming crystalline substances indicates the proportion of different atoms.
Valence
Valence is an integer that expresses the ability of an atom to combine with others.
Formulation of Binary Compounds
To formulate binary compounds, the symbols of the elements forming the compound are written in the same order as they appear in the periodic table. The valences of the elements are exchanged and written as subscripts. Greek prefixes are used to indicate the number of atoms of each class.
Spanish Golden Age Drama
The Domestic Comedy
In the 17th century, courtly dramas and comedies were created in Spain. The hallmark theatrical formula of this period is the “national comedy” or “new comedy.”
Techniques
- Plays are divided into acts.
- Tragic and comic elements are mixed.
- There are temporary changes of place.
- Two parallel actions are presented.
- Plays are written in verse.
Themes
Love, uncontrollable passion, honor, and religion.
Characters
The gallant and the lady, the father or brother of the lady, the jester, the powerful, and above all, the king.
Lope de Vega
Lope de Vega created a theatrical formula capable of engaging all social classes. He is the creator of the national comedy.
Characteristics of Lope’s Theater
His plays are inspired by national novels, songs, etc. They are characterized by the dominance of action, which develops rapidly. There are many characters.
Calderon de la Barca
Calderon de la Barca was the last playwright of this period.
Characteristics of Calderon’s Theater
His theater is more aristocratic than Lope’s, more complex, and aimed at a cultured minority. His work addresses the brevity of life and man’s ability to be free. Characters are inclined to introversion. Notable dramas include The Mayor of Zalamea and Life is a Dream.