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1- Review sheet for Building Blocks of Molecules2.1 Atoms, Isotopes, Ions, and Molecules1.Definition of matter. Matter is any substance that occupies space and has mass.2.Definition of elements. Elements are unique forms of matter with specific chemical and physicalproperties that cannot be broken down into smaller substances by ordinary chemical reactions. There are118 elements, but only 92 occur naturally. The remaining elements are synthesized in laboratories and areunstable3.How are elements designated? Each element is designated by its chemical symbol, which is a singlecapital letter or, when the first letter is already “taken” by another element, a combination of two letters4.What are the four elements common to all living organisms? The four elements common to all livingorganisms are oxygen (O), carbon (C), hydrogen (H), and nitrogen (N). In the nonliving world, elementsare found in different proportions, and some elements common to living organisms are relatively rare onthe earth as a whole5.Definition of atom. An atom is the smallest unit of matter that retains all of the chemical properties of anelement.6.The atom is composed into what two regions and what are found in each of those regions?The nucleus and the outermost region. Contain protons, neutrons and electrons.7.How is hydrogen (H) unique in terms of its subatomic particles? It contains no neutrons only oneelectron and one proton.8.Electrons are found in _orbit__________ surrounding the nucleus.9.How do we designate the mass of a proton or a neutron? Approximately the same mass or one Dalton.1.67X10 -2410.How do protons and neutron differ from each other? In their electric charge. A proton is positivelycharged whereas a neutron is uncharged.11.Based on the answer to #10, what contribution does a neutron make to an atom? the number ofneutrons in an atom contributes significantly to its mass, but not to its charge.12.What role do electrons have in contributing to an atom’s mass?they do not contributemuch to an element’s overall atomic mass. Therefore, when considering atomic mass, it is customary toignore the mass of any electrons and calculate the atom’s mass based on the number of protons andneutrons alone.13.Do electrons carry a charge?If so, how can that charge be measured? Each electron has a negativecharge equal to the positive charge of a proton.In uncharged, neutral atoms, the number of electronsorbiting the nucleus is equal to the number of protons inside the nucleus. In these atoms, the positive andnegative charges cancel each other out, leading to an atom with no net charge.