Biology campbell chapter 2

Chapter 2 Terms Matter – anything that takes up space and has mass. Element – substance that cannot be broken down to other substances by chemical reactions. Compound – substance consisting of two or more different elements combined in a fixed ratio. Essential Element – the 20-25% of the 92 natural elements an organism needs to live a health life and reproduce. Trace Elements – required by an organism only minute quantities. Atom – the smallest unit of matter that still retains the properties of an element. Neutrons – electrically neutral Protons – one unit of positive charge Electrons – one unit of negative charge Atomic Nucleus – the center of an atom Dalton – the same as the atomic mass unit or amu. Atomic Number – the number of protons, which is unique to that element Mass Number – the sum of protons plus neutron in the nucleus of an atom. Atomic Mass – the total mass of an atom. Isotopes – different atomic forms of the same element. Radioactive Isotope – one in which the nucleus decays spontaneously, giving off particles and energy. Energy – defined as the capacity to cause change for instance, by doing work. Potential Energy – the energy that matter possesses because of its location or structure. Electron Shells – each with a characteristic average distance and energy level. Valence Electrons – the electrons in the outermost electron shell. Valence Shell – the outermost electron shell. Orbital – the three-dimensional space where an electron is found 90% of the time. Chemical Bonds – the interaction of sharing or transferring valence electrons, which result in staying close together. Covalent Bond – the sharing of a pair of valence electrons by two atoms. Molecule – two or more atoms held together by covalent bond. Single Bond – a pair of shared electrons Double bond – two pairs of valence electrons are shared. Valence – the bonding capacity of an element. Electronegativity 0 the attraction of a particular atom for the electrons of a covalent bond. Non-polar Covalent Bond – Polar Covalent Bond – Ion – a charged atom or molecule Cation – A positive ion. Anion – A negative ion. Ionic Bond – when cations and anions attract each other. Ionic Compounds – compounds formed by ionic bonds, salt. Hydrogen Bond – non-covalent attraction between a hydrogen and an electronegative atom Van Der Waals Interactions – Chemical Reactions – the making and breaking of chemical bonds, leading to changes in the composition of matter. Reactants – Products – Chemical Equilibrium – the point at which the reactions offset one another exactly. Chapter 2 Review: In the term trace element, the adjective trace means that The element is required in very small amounts