BackThe Chemical Context of Life: Elements, Atoms, and Compounds
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
The Chemical Context of Life
Elements and Atoms
Understanding the chemical basis of life begins with the study of elements and atoms, which are the fundamental building blocks of matter.
Element: A substance that cannot be broken down into another substance by chemical means.
Atomic Number: The number of protons in an atom, which distinguishes one element from another. Atoms also contain neutrons and electrons.
Electron Shells: Electrons are arranged in shells around the nucleus. The arrangement of electrons determines how atoms interact and bond with each other.
Valence Electrons: Electrons in the outermost shell are called valence electrons. These are involved in forming bonds with other atoms.
Octet Rule: Elements strive to have a full outer shell (usually 8 electrons) to achieve stability, leading to the formation of compounds or molecules.
Example: Oxygen, carbon, hydrogen, and nitrogen are the most common elements in living organisms, making up about 96% of living matter.
Electron Shells and Orbitals
Atoms have a specific arrangement of electrons in shells and orbitals, which influences their chemical behavior.
First Shell: Contains one s orbital (1s orbital) and can hold up to 2 electrons.
Second Shell: Contains one s orbital (2s orbital) and three p orbitals (2p orbitals), holding up to 8 electrons in total.
Additional info: The arrangement of electrons in these shells determines how atoms bond and interact with each other.
Compounds and Molecules
Atoms combine to form compounds and molecules, which are essential for biological processes.
Compound: A substance consisting of two or more elements combined in a fixed ratio.
Molecule: Two or more atoms held together by chemical bonds.
Compounds are held together by energy in a stable association.
Example: Sodium (Na) and chlorine (Cl) combine to form sodium chloride (NaCl), a common table salt.
Equation:
Additional info: Chemical bonds, such as ionic and covalent bonds, are responsible for holding atoms together in compounds.
