Atomic Structure Basics

Atomic Structure and Electron Configuration

• The most likely location for an electron relative to its nucleus is described as an "orbital."
• Each orbital can hold a maximum of two electrons.
• The element with an atomic number of 16 is sulfur (S).
• The maximum number of electrons a shell can host is determined by the formula 2n², where n is the shell number.
• Bonding in an atom is primarily determined by electrons, specifically valence electrons.
• The term "valence shell" refers to the outermost occupied shell of an atom.
• The element with an atomic weight of 39.10 is potassium (K).
• Electrons in an atom move in defined energy levels or orbitals and do not travel in fixed paths.

Atomic Composition and Identity

• Most of an atom's mass is concentrated in the nucleus, which contains protons and neutrons.
• The unique identity of each element is defined by its atomic number, which indicates the number of protons it possesses.
• When the number of protons equals the number of electrons, the atom is electrically neutral.
• An ion is an atom or molecule that has gained or lost one or more electrons, resulting in a net charge.
• Hydroxide (OH-) is an example of a negative ion, known as an anion.

Atomic Structure and Isotopes

• The total number of protons and neutrons in an atom's nucleus is called the "mass number."
• Isotopes differ in the number of neutrons they contain while having the same number of protons.
• A common chemical found in the human body that aids in hair formation is keratin.

Plant Defense and Interactions

• Chemical compounds can be utilized by plants to inhibit the growth of other nearby trees, often referred to as allelopathic compounds.
• Pheromones play a crucial role in communication for some reptiles, aiding in mating and territorial behaviors.
• Plants deploy secondary metabolites as part of their defense strategy against herbivores and competing plants.
• Chemicals released by the chili pepper tree primarily function to deter herbivores.

Chemical Warfare and Ecosystem Impact

• The primary purpose of chemical warfare in plants includes defense against herbivory and competition.
• The release of chemicals by the Black walnut tree can negatively affect surrounding plants, inhibiting their growth.

Animal Behavior and Survival

• Some animals use pheromones for survival by marking territories or attracting mates.

Fundamental Atomic Properties

• The mass number is the sum of protons and neutrons in the nucleus, whereas the atomic number only counts protons.
• Different forms of a single element are known as isotopes.
• Atomic weight represents the average mass of an element's isotopes relative to a standard.
• Radioactive isotopes are characterized by instability and emissions of radiation.
• The half-life of a radioactive isotope is the time required for half of the substance to decay.
• Radioactive isotopes share the same fundamental properties as stable isotopes, differing mainly in stability.

Molecular Composition

• Molecules consist of two or more atoms bonded together.
• Compounds are specific types of molecules formed by the chemical combination of different elements.
• The four most abundant bulk elements in living organisms are carbon, hydrogen, oxygen, and nitrogen.

Nutritional Aspects and Functions

• An iron-poor diet can lead to a decrease in red blood cell production, causing anemia.
• Iodine plays a vital role in thyroid function within the diet.
• Essential elements for life, found in significant amounts, include carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur.
• Red blood cells function primarily to transport oxygen throughout the body.
• A chemical element is a substance that cannot be broken down into simpler substances by chemical means.
• Trace elements like iron and zinc are crucial for various physiological functions despite being required in smaller amounts.