Chemical Elements, Periodic Table, and Bonding Principles
Natural and Artificial Elements
There are approximately 90 naturally occurring elements. Necessary equipment in physics laboratories has allowed for the creation of additional, artificial elements. Few elements are found in their free state in nature; they are mainly found combined with other elements, forming compounds.
Element Distribution
Elements in the Earth’s Crust and Core
The element iron is abundant but primarily found in the Earth’s core. The Earth’s crust is mainly composed of oxygen and
Read MoreConcise Chemistry: Atomic Mass, Radiation, Water & Polymers
Atomic Structure and Radiation
- The relative atomic mass, Ar, or atomic mass, is the mass of an atom measured by comparison with the carbon atom -12.
- Alpha Particles: consist of two protons and two neutrons, i.e., are nuclei of helium atoms. When a radioactive nucleus emits an alpha particle, it is transformed into another with mass number A-4 and atomic number Z-2.
- Beta particles: are very fast electrons. They result from the disintegration of neutrons into a proton and an electron. When emitted, the
States of Matter: Properties, Kinetic Theory, and Elements
States of Matter: Properties and Characteristics
Solids
Solids have a definite mass, shape, and volume. They are generally difficult to compress, and their density is close to that of liquids. Key properties include elasticity, fragility, and hardness.
Liquids
Liquids have a definite mass and volume but take the shape of their container. They are difficult to compress and expand when heated. Important properties include surface tension, capillarity, and viscosity.
Gases
Gases have a definite mass but
Read MoreNitrates and Carbonates: Properties, Formation, and Environmental Impact
Nitrates: Properties and Formation
Nitrates: Nitrates are salts derived from nitric acid. They are formed by the junction of the nitrate anion (NO3–) with a metal. They are less abundant than carbonates and are characterized by their high solubility and a structure similar to carbonates. Nitrates are an essential part of fertilizers. Plants convert them back into organic nitrogen compounds such as amino acids.
Inorganic nitrates are formed in nature by the decomposition of nitrogenous compounds such
Read MoreCarbohydrate Reactions: Qualitative Tests
1. Molisch Test
Concentrated sulfuric acid (H2SO4) dehydrates monosaccharides, forming furfural (from pentoses) or 5-hydroxymethylfurfural (from hexoses). These aldehydes condense with α-naphthol to produce a purple ring. This test is positive for all free or combined carbohydrates (mono-, oligo-, and polysaccharides).
Reaction: Carbohydrate + α-naphthol + H2SO4 → Purple product (Molisch)
Reagents:
- Concentrated sulfuric acid
- Molisch reagent: 5g α-naphthol in 100mL ethanol
Procedure:
- Tube A: 2mL of
Chemistry Principles: Matter, Mixtures, and Laws
Principles of Chemistry
Matter and Chemistry
Mass is the fundamental characteristic of matter.
Chemistry is for studying the nature of matter and changes that affect nature.
Physical changes do not alter the nature of substances; chemical changes do.
Pure Substance
A pure substance has a definite, constant composition, specific physical and chemical characteristics, and cannot be separated into other substances by physical methods.
Mixture
A mixture has variable composition and properties related to its
Read More