Chemical Properties and Reactions: Elements, Compounds, and Laws

Posted on Dec 8, 2024 in Chemistry

Periodic Properties of Elements

Atomic Radius

The atomic radius is the distance from the center of the nucleus to the area corresponding to the outermost level. Over a period, the radius decreases from left to right.

Ionization Energy

Ionization energy is the energy required to form an ion (cation); the energy that must be delivered to an isolated atom to remove an electron. The ionization increases from left to right, and in a group, it decreases from top to bottom.

Electronegativity

Electronegativity is the ability to attract electrons in a bond. Electronegativity increases from left to right and decreases from top to bottom.

Lewis and Kossel Theories

Lewis Theory

Inert gases are stable with 8 electrons in their outer orbit. Helium saturates its only orbit with 2 electrons. They are stable and monatomic.

Kossel Theory

Metals and nonmetals with less than 8 electrons in their outer shell join together to form molecules. This is due to the need to acquire the electronic configuration of the nearest noble gas in the periodic table. In this process, they win, lose, or share electrons.

Ions and Bonding

When atoms of a metal and a nonmetal combine, there is a transfer of electrons. They are held together by electrostatic forces.

Properties of Ionic Compounds

  • High melting and boiling points.
  • Solid at room temperature.
  • Do not conduct electrical current in solution.
  • Conduct electrical current when molten.
  • Hard and brittle in the solid state.

Properties of Covalent Compounds

  • Do not conduct electrical current.
  • Low melting and boiling points because the forces holding the molecules together are weak.
  • Soluble in organic solvents and insoluble in water.
  • Form crystal structures, atomic and molecular.

Properties of Metallic Compounds

  • Have characteristic brightness.
  • Conduct electrical current.
  • Ductile and malleable.
  • Insoluble in water, do not dissolve in any known solvent.

Use of Hydroxides

Potassium Hydroxide (KOH)

Used in soap production, potassium, and reagent production.

Sodium Hydroxide (NaOH)

Used in the production of soap, dyes, and paper; repair of organic acids, alcohols, and lights in the laboratory; oil and rubber.

Calcium Hydroxide (Ca(OH)2)

In salt water, it is called lime water. Mixed with sand or mortar, it forms organo. It binds to bricks and sets due to setting or hardening.

Aluminum Hydroxide (Al(OH)3)

Used in purifying waters of the Río de la Plata. Aluminum sulfate and lime water are added, forming aluminum hydroxide, which carries suspended particles and absorbs water. It is used for dyeing.

Magnesium Hydroxide (Mg(OH)2)

Used on tape, wire, or powder. Mixed with potassium chlorate, magnesium is used for taking pictures in artificial light. It is used in alloys such as aluminum chloride and the target electron.

Ternary Acids

Nitric Acid

  • Used in the manufacture of sulfuric acid.
  • Used to prepare nitrobenzene, aniline, and TNT.
  • Used to prepare cotton or cellulose nitrate powder.
  • Used in photography with parakeet acid and silver nitrate.
  • Used for its oxidizing action.

Sulfuric Acid

  • Used with hydrochloric acid.
  • Used to produce chlorine.
  • Used to produce hydrogen.
  • Used to produce nitric acid.
  • Used in fertilizers.
  • Used in coloring and dyes.
  • Used in glass and ink.

Gas Laws

Boyle’s Law

The volume of a given mass of gas at constant temperature is inversely proportional to the pressure of the gas. P1 x V1 = P2 x V2

Charles’s and Gay-Lussac’s Law

The volume of a given mass of gas at constant pressure is proportional to its absolute temperature. V1 / T1 = V2 / T2

Combined Gas Law

Constant Volume: P1V1 / T1 = P2V2 / T2

Stoichiometry

Stoichiometry is the study of the quantitative relationships between atoms that make up substances and those obtained in a chemical reaction.

Quantitative Reactions

  • Chemical formula of substances, solving problems that link the percentage composition of a substance with its chemical formula.
  • Chemical equation representing chemical reactions: formula, minimum number of particles that are part of the reaction, the masses, the number of moles, and volumes of substances involved in the reaction.

Theory of Acids and Bases: Brønsted-Lowry

Thomas M. Lowry and Johannes Brønsted announced that experiments with acids and bases in solution challenged the traditional definition of unrelated acids and bases to create a new concept of conjugate acid-base systems.

Brønsted-Lowry Definitions

  • A Brønsted-Lowry acid is a proton donor, it donates a hydrogen ion, H+.
  • A Brønsted-Lowry base is a proton acceptor, it accepts a hydrogen ion, H+.

The concept of acid and base by Brønsted and Lowry helps explain why a strong acid displaces another weak compound. Acid-base reactions are viewed as a competition for protons. In a chemical equation, the following reaction of Acid (1) with Base (2):

Acid (1) + Base (2) ⇌ Acid (2) + Base (1)

The balance equation is described which can be moved left or right. The reaction takes place in the direction which produces the weaker acid-base pair. For example:

HCl + H2O ⇌ H3O+ + Cl–

In contrast, hydrogen fluoride (HF) is a weak acid in water and does not easily transfer a proton to water:

HF + H2O ⇌ H3O+ + F–

The Brønsted-Lowry theory also explains that water can display amphoteric properties, meaning it can react with both acids and bases. Water acts as a base in the presence of an acid stronger than itself (like HCl) or an acid with a greater tendency to dissociate than water:

HCl + H2O ⇌ H3O+ + Cl–

Water also acts as an acid in the presence of a stronger base than itself (like ammonia):

NH3 + H2O ⇌ NH4+ + OH–