AC-HPAT Chemistry Key Questions and Correct Answers

single displacement - A + BC -- AC + B double displacement - AB + CD -- AD + CB precipitate - A solid that forms from a solution during a chemical reaction. energy level - Energy levels (also called electron shells) are fixed distances from the nucleus of an atom where electrons may be found. What is the atomic number of an element - number of protons What is the mass number of an element - The number of protons and neutrons in the nucleus of an atom. Together, the number of protons and the number of neutrons determine an element's mass number: mass number = protons + neutrons. If you want to calculate how many neutrons an atom has, you can simply subtract the number of protons, or atomic number, from the mass number. Isotopes - Atoms of the same element that have different numbers of neutrons Radio isotopes - unstable isotopes Difference between radioisotopes and isotopes - The key difference between isotopes and radioisotopes is that isotopes may or may not undergo radioactive decay whereas radioisotopes essentially undergo radioactive decay. synthesis reaction - a reaction in which two or more substances combine to form a new compound decomposition reaction - a reaction in which a single compound breaks down to form two or more simpler substances Concept of quanta of energy - In 1913, Niels Bohr proposed a theory for the hydrogen atom, based on quantum theory that some physical quantities only take discrete values. Electrons move around a nucleus, but only in prescribed orbits, and If electrons jump to a lower-energy orbit, the difference is sent out as radiation. What is organic chemistry? - the study of carbon compounds Electronegativity - A measure of the ability of an atom in a chemical compound to attract electrons covalent bond - A chemical bond that involves sharing a pair of electrons between atoms in a molecule functional groups - the components of organic molecules that are most commonly involved in chemical reactions