Mastering biology chapter 2 Flashcards
Mastering biology chapter 2
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What is an element? A substance that cannot be broken down into other substances by chemical reactions. What is the smallest unit of matter that retains the properties of an element? An atom. What are the four most common elements in living organisms? Carbon, hydrogen, oxygen, and nitrogen. What is a compound? A substance consisting of two or more elements in a fixed ratio. What is the significance of trace elements? They are required by an organism in only minute quantities but are essential for life. What is an isotope? Atoms of the same element with different numbers of neutrons. What is a covalent bond? A chemical bond formed by the sharing of electron pairs between atoms. What is an ionic bond? A chemical bond resulting from the attraction between oppositely charged ions. What is electronegativity? The ability of an atom to attract electrons in a covalent bond. What is a hydrogen bond? A weak bond between two molecules resulting from an electrostatic attraction. What is the role of valence electrons in chemical bonding? They determine how atoms interact and bond with each other. What is a polar covalent bond? A covalent bond in which electrons are shared unequally. What is a molecule? Two or more atoms held together by covalent bonds. What is the difference between a molecule and a compound? A molecule is two or more atoms bonded together; a compound is a molecule with different elements. What is the atomic number of an element? The number of protons in the nucleus of an atom. What is the mass number of an atom? The sum of protons and neutrons in the nucleus. What is a chemical reaction? The process of making and breaking chemical bonds, leading to changes in the composition of matter. What is a reactant in a chemical reaction? A starting material in a chemical reaction. What is a product in a chemical reaction? A substance formed as a result of a chemical reaction. What is the law of conservation of mass? Matter is not created or destroyed in a chemical reaction.