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CHEM111 Ch 2
| Term | Definition |
|---|---|
| Atoms | The smallest unit of an element that have all the properties of that element |
| Element | Composed entirely of one type of atom |
| Compound | Two or more different elements |
| Law of constant composition | All samples of a pure substance contain the same elements in the same proportion by mass |
| Law of multiple proportions | When the same elements from more than one compound, the mass of one element that combines with a fixed mass of a second element are in a ratio of small whole numbers |
| Law of conversion of mass | There is no detectable change in mass when a chemical reaction occurs |
| Electrons | Negatively charged; charge can change |
| Protons | Positively charged; account for the charge on the nucleus of all atoms; cannot change w/o changing atom identity |
| Neutrons | Neutral particle; can change, results in isotopes of our atom after mass number |
| Atomic number | Number of protons in the nucleus of an atom |
| Mass number | The sum of protons and neutrons in the nucleus |
| Isotopes | Atoms of an element whose nuclei contain different numbers of neutrons |
| Ions | Atoms gain or lose electrons producing particles called ions |
| Cations | Positively charged and forms when an atom loses at least one electron |
| Anion | Negatively charged and forms when an atom gains at least one electron |
| Atomic mass | A relative mass scale has been established to express the masses of atoms |
| Atomic mass formula | Atomic mass = fraction a x isotopic mass a + fraction b x isotopic mass b |
| Period (on a periodic table) | A horizontal row |
| Group (on a periodic table) | A vertical column containing chemically similar elements |
| Metal (on a periodic table) | An element that is shiny and is a good electrical conductor; metallic elements are on the center and left side of the periodic table |
| Nonmetal (on a periodic table) | An element that is typically a nonconductor; nonmetals are on the top right of the periodic table |
| Metalloid (on a periodic table) | An element that has properties of both metals and nonmetals; metalloids are found on the staircase separating metals and nonmetals on the periodic table |
| Representative elements (on the periodic table) | The elements in the A groups (1A-8A) or 1,2 13-18 |
| Transition metals (on the periodic table) | The elements in the B groups (1B-8B or 3-12) |
| Inner transition metals (on the periodic table) | The two rows of metals (lanthanides and actinides) set at the bottom of the periodic table |
| Alkali metals (on the periodic table) | Soft, reactive metals in group 1A (1) |
| Alkaline Earth metals (on the periodic table) | Elements in group 2A (2) |
| Halogens (on the periodic table) | Reactive nonmetals in group 7A (17) AKA salt-formers |
| Noble gases (on the periodic table) | The stable, largely inert gases in group 8A (18) |
| Molecule | A combination of atoms so strongly that they behave as a single particle (ex: CO2 -- carbon dioxide) |
| Diatomic molecules | They contain 2 atoms |
| Homonuclear diatomics | Contain 2 of the SAME atom (ex: N2 -- nitrogen gas) |
| Heteronuclear diatomics | Contain 2 DIFFERENT atoms (ex: NO -- nitrogen monoxide) |
| Molecular formula | Shows the number of every type of atom in the molecule |
| Structural formula | Shows how the atoms are connected in the molecule |
| Molecular mass | The sum of the atomic masses of all atoms in the molecular formula |
| Ionic compound | Composed of cations and anions forming a neutral species (typically metals & nonmetals) |
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