Atoms, Bonds, and Molecules

Atoms, Bonds, and Molecules

• Matter is all tangible materials that occupy space and have mass.
• An atom is a tiny particle that cannot be subdivided into smaller substances without losing its properties.

Properties of Atoms

• Protons (p+) are positively charged and found in the nucleus.
• Neutrons (n°) have no charge and are also found in the nucleus.
• Electrons (e-) are negatively charged and surround the nucleus

Elements

• An element is an atom with a characteristic atomic structure and predictable chemical behavior.
• Isotopes are variant forms of the same element that differ in the number of neutrons.
• Radioactive isotopes have unstable nuclei that spontaneously release energy in the form of radiation, they are used in research and medical applications.

Key Elements and Their Significance

• Calcium (Ca): Atomic mass is 40.1, ionized form is Ca2+, part of outer covering of certain shelled amoebas or stored within bacteria.
• Carbon (C): Atomic mass is 12.0, ionized form is CO32-, is the principal structural component of biological molecules.
• Carbon-14 (C-14): Atomic mass is 14.0, is a radioactive isotope used in dating fossils.
• Chlorine (Cl): Atomic mass is 35.5, ionized form is CO-, is a component of disinfectants used in water purification
• Cobalt (Co): Atomic mass is 58.9, ionized form is Cr, a trace element needed by some bacteria to synthesize vitamins.
• Cobalt-60 (Co-60): Atomic mass is 60, ionized forms are Co2+ and Co3+, emits gamma rays, and is used in food sterilization and to treat cancer.
• Copper (Cu): Atomic mass is 63.5, ionized forms are Co2+ and Co3+, necessary for the function of some enzymes, and copper salts are used to treat fungal and worm infections.
• Hydrogen (H): Atomic mass is 1, ionized form is H+, necessary component of water and many organic molecules, H₂ gas released by bacterial metabolism.
• Hydrogen (H3): Atomic mass is 3, ionized form is H+, has two neutrons, radioactive, used in clinical laboratory procedures
• Iodine (I): Atomic mass is 126.9, ionized from is Γ, a component of antiseptics and disinfectants and is used in the Gram stain
• Iodine (I-131, I-125): Atomic mass is 131, 125, ionized from Γ, radioactive isotopes for diagnosis and treatment of cancers.
• Iron (Fe): Atomic mass is 55.8, ionized forms are Fe2+ and Fe3+, a necessary component of respiratory enzymes required by microbes to produce toxin.
• Magnesium (Mg): Atomic mass is 24.3, ionized form is Mg, trace element needed for some enzymes and component of chlorophyll pigment.
• Manganese (Mn): Atomic mass is 54.9, ionized form is Mg2+, a trace element for certain respiratory enzymes
• Nitrogen (N): Atomic mass is 14.0, ionized forms are Mn2+ and Mn3+, a component of all proteins and nucleic acids; the major atmospheric gas, and NO3-
• Oxygen (O): Atomic mass is 16.0, An essential component of many organic molecules; molecule used in metabolism by many organisms.
• Phosphorus (P): Atomic mass is 31, ionized from is PO43-, A component of ATP, nucleic acids, cell membranes; stored in granules in cells.
• Phosphorus (P-32): Atomic mass is 32, ionized from is PO43-, A radioactive isotope used as a diagnostic and therapeutic agent.

More Key Elements and Their Significance

• Potassium (K): Atomic mass is 39.1, ionized form is K+, Required for normal ribosome function and protein synthesis; essential for cell membrane permeability.
• Sodium (Na): Atomic mass is 23.0, ionized from is Na+, Necessary for transport; maintains osmotic pressure; used in food preservation.
• Sulfur (S): Atomic mass is 32.1, ionized from is SO4, Important component of proteins; makes disulfide bonds; storage element in many bacteria.
• Zinc (Zn): Atomic mass is 65.4, ionized from is Zn2+, An enzyme cofactor; required for protein synthesis and cell division; important in regulating DNA.
• Pathways in which electrons rotate around the nucleus
• Represent volumes of space in which an electron is likely to be found

Bonds and Molecules

• A molecule is a chemical substance that results from the combination of two or more atoms (e.g., O2, N2).
• A compound is a molecule composed of two or more different elements (e.g., H2O, C6H12O6).
• Chemical bonds result when two or more atoms share, donate (lose), or accept (gain) electrons.
• Valence is the number of electrons in the outermost shell of an element.
• Valence determines the degree of reactivity and the type of bonds an element can make.

Covalent Bonds

• Form between atoms that share electrons rather than donating or receiving them.
• Single covalent bonds share a pair of electrons (H2).
• Double covalent bonds share two pairs of electrons and are more rigid than single bonds (O2).

Polar and Nonpolar Molecules

• Polar molecules result when a molecule is formed between two atoms that have different electronegativity or ability to attract electrons.
• Nonpolar molecules are formed when atoms have similar electronegativity.