Elements and Compounds

Elements Can not be broken down by chemical means Chemical alphabet Building blocks First 92, 88 occur in nature w/ exception of plutonium, above 92, they are synthesized

Atom Smallest unit of an element that retains the characteristics of that element Smallest unit of an element that can enter into a chemical reaction Contain sub-particles

Distribution of Elements

Rules for Element Symbols Symbols have one or two letters If one letter, capitalize it If two, only capitalize the first

Periodic Table Increasing atomic number Left to right Mendeleev Similar chemical properties in families

Metals and Nonmetals Metals Nonmetals Not lustrous Poor conductors Solid at room temp (except Hg) Lustrous Good conductors Malleable Ductile High melting point High density Don’t commonly combine with other metals but when they do, they form alloys Commonly combine with nonmetals to form minerals, chlorides, oxides and sulfides Not lustrous Poor conductors Low melting points Low densities Can be solid liquid or gas Form molecular compounds when combined with each other

Metalloids Boron, silicon, geranium, arsenic antimony, tellurium and polonium Properties of both metals and nonmetals

Diatomics H2 N2 O2 F2 Cl2 Br2 I2

Compound Substance containing two or more elements Can be broken down Atoms of the elements in a compound are combined in whole number ratios Molecular and ionic compounds

Compounds Molecular Ionic Smallest uncharged individual unit of a compound formed by the union of two or more atoms water Positively or negatively charged group of atoms or atom Held together by the attractive forces between ions or groups of ions Ions are negatively (anion) or positively (cation) charged Sodium chloride

Chemical Formulas Abbreviations Shows symbols and abbreviations of atoms of elements in compound Subscripts are used to indicate numbers of atoms of elements present in compound Subscripts are the small numbers partially below H2O 2 hydrogen atoms, 1 oxygen atom