Science Flashcards: Molecule Definition

Molecule

• A molecule is formed by two or more atoms bonded together through chemical bonds.
• Represents the smallest unit of a compound.
• Can consist of identical atoms (e.g., O2) or different atoms (e.g., H2O with 2 hydrogen and 1 oxygen).

Atom

• Introduced by John Dalton in 1802 through atomic theory.
• Atoms are indivisible and cannot be broken into smaller parts.
• Atoms of an element are identical, maintaining the element's properties.

Proton

• Protons are positively charged particles found in an atom's nucleus.
• Atoms are incredibly small, with a single grain of sand containing more atoms than grains of sand on a beach.

Electron

• Electrons are negatively charged particles that rapidly orbit the nucleus.
• They are energetic and move in various directions around the nucleus.

Chemical

• A chemical symbol is a shorthand representation of an element, composed of one or two letters.
• The first letter is always uppercase; if a second letter is present, it is always lowercase (e.g., Na for sodium).

Chemical Formula

• A chemical formula combines symbols to represent a compound (e.g., NaCl for sodium chloride).
• It indicates the ratio of elements present in the compound.

Chemical Equation

• Represents a chemical reaction using symbols and formulas.
• Illustrates both reactants and products, similar to a mathematical equation with an "=" sign.

Coefficient

• The number placed before a chemical symbol/formula in an equation.
• Indicates how many molecules are involved in the reaction.

Subscript

• A number positioned lower right of a chemical symbol.
• Specifies the number of atoms of an element within a compound.

Atomic Number

• The count of protons in an atom's nucleus determines the atomic number.
• Organizes elements on the periodic table; for example, copper has an atomic number of 29.

Atomic Mass

• Calculated as the sum of protons and neutrons in an atom's nucleus.

Energy Levels

• Refers to specific locations where electrons are arranged around the nucleus.
• The arrangement of electrons influences an element's chemical properties.

Protons and Electrons

• In neutral elements, the number of protons equals the number of electrons.
• Example: Oxygen, with 8 protons, also has 8 electrons.

Chemical Reaction

• A process in which substances transform into different substances without matter being created or destroyed.
• The mass of reactants equates to the mass of products (e.g., CH4 + 2O2 → CO2 + 2H2O).

Neutron

• Neutrons are neutral particles found in an atom's nucleus (specific details not provided).