Bio 101 NVCC Exam 1 TEST WITH VERIFIED ANSWERS

Bio 101 NVCC Exam 1 TEST WITH VERIFIED ANSWERS Matter - ANSWER organisms are composed of matter Element - ANSWER - A substance that cannot be broken down to other substances by chemical reactions - Oxygen, carbon, and hydrogen make up 96.3% of the body - An element's properties depend on the structure of its atoms Compound - ANSWER A substance consisting of two or more elements in a fixed ratio Trace elements - ANSWER required by an organism in only minute quantities Atoms - ANSWER the smallest unit of matter that still contains properties of an element Protons - ANSWER - Positively charged particles - The negative and positive protons hold the atom together - # of protons = # of neutrons = # of electrons Neutrons - ANSWER the particles of the nucleus that have no charge Electrons - ANSWER Negatively charged particles atomic number - ANSWER the number of protons in an atom mass number - ANSWER the sum of the number of neutrons and protons in an atomic nucleus Isotopes - ANSWER - Atoms of the same element that have different numbers of neutrons - Used for dating fossils, tracking atoms through metabolic processes, and diagnosing medical disorders radioactive isotope - ANSWER An isotope whose nucleus decays spontaneously, giving off particles and energy. electron shells (energy levels) - ANSWER - First shell: 2 electrons - Second shell: 8 electrons - Third shell: 8 electrons - energy levels of shells increase with distance from the nucleus valence shell - ANSWER The outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom. valence electrons - ANSWER Electrons on the outermost energy level of an atom covalent bond - ANSWER - A chemical bond that involves sharing a pair of electrons between atoms in a molecule - shared electrons count as part of each atom's valence shell - 2 or more atoms held together by covalent bonds constitute a molecule