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Periodic Table - 2 An element is a type of atom that is distinguished by its atomic number; The number above the letter stands for 3 things in a neutral atom (atomic number, number of protons and number of electrons) Compounds chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by mass H2 is not a compound since it is made up of only 1 element. NaCl (salt) is a compound. Molecules A molecule is defined as a sufficiently stable electrically neutral group of at least two atoms in a definite arrangement held together by strong chemical bonds It may consist (made up) of atoms of the same chemical element, as with oxygen (O2), or of different elements, as with water (H2O). When 2 elements from the right side of the Periodic table get together, it is called a molecule Mixtures Mixtures can be homogeneous or heterogeneous. Homogeneous = Looks same throughout (solutions like – salt water Heterogeneous = Looks different throughout (granola cereal/salad) Solutions A solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent. common examples ( salt or sugar dissolved in water, a liquid. Gases may dissolve in liquids also carbon dioxide or oxygen in water. Colloid A colloid is a type of mechanical mixture where one substance is dispersed evenly throughout another. A colloidal system may be solid, liquid, or gaseous. fog, mist, milk, mayonnaise, hand cream, whipped cream, butter, gelatin, jelly, cheese, opal, paint, pigmented ink, smoke, air particulates Suspension A suspension is a heterogenous fluid containing solid particles that are sufficiently large for sedimentation Mud or muddy water, is where soil, clay, or silt particles in water Flour suspended in water Fog water suspended in air. Paint Chalk powder suspended in water. Dust particles suspended in air. Period/Row Another word for rows are periods. The periods (rows) go side to side on a Periodic Table. Group/Family There are 18 groups on the Periodic Table. Groups are also called families or columns…….(goes up and down). Groups (families) share characteristics just like you share characteristics with your family. They bond the same way since they have the same amount of valence electrons. Periodic Table The modern periodic table arrangement was made by a Russian chemist named Dmitri Mendeleev in 1869. The current standard table contains 117 confirmed elements as of January 27, 2008 The elements on the Periodic table are in order of increasing atomic number. Charges Neutral atoms have no charge. When atoms are not neutral, they have a charge. When atoms have a charge, they bond or get together with other atoms to go to a neutral state. Noble gases are always neutral. They do not have charges. They do not bond with other elements. They are happy by themselves. Alkali Metals Group 1 is the alkali metals (+1 Charge) (Lithium, Sodium, Potassium, Rubidium, Cesium, Francium)