Physical Science Pre-Test Chapter 19 Each letter or pair of letters is a _______ _______. Chemical symbol Know your chemical symbols and chemical names. compound A _______ is a combination of two or more elements. subscript _______ means written below. What two things does a chemical formula tell? Chemical _______ formula _______ tells which elements and the ratio of the atoms of those elements. An element is Chemically stable _______ _______ if the outer energy level is completely filled. 8 _______ is the maximum number of electrons in an elements outermost energy level. Chemical bond _______ _______ is a force that holds together the atoms in a substance. Does a compound always have the same properties as the elements that make it up? NO Valence electrons _______ _______ are the electrons in the outermost energy level. Noble _______ are gases _______ more chemically stable than other elements because they have a complete outer energy level. Why do most elements tend to form compounds? To become chemically stable Ions _______ are atoms that have a charge. Ionic bond _______ _______ is the force of attraction between the opposite charges of the ions in an ionic compound. The result of bonding is a net charge of zero ________. cation _______ is a positively charged ion. anion _______ is a negatively charged ion. Covalent _______ _______ bonds is the attraction that forms between atoms when they share electrons. polar _______ means “having oppositely charged ends.” Polar molecule _______ _______ is a molecule that has a positive end and a negative end. Nonpolar molecule _______ _______ is a molecule that does not have oppositely charged ends. Oxidation number _______ _______ is the apparent charge on an element. Oxidation number _______ _______ is a positive or negative number assigned to an element to show its combining ability in a compound. Left to Right across the periodic table, the number of valence electrons goes __________. 1, 2, 3, 4, 5, 6, 7, 8 Left to Right across the periodic table, oxidation numbers go +1, +2, +3, ±4, -3, -2, -1, 0 _______________ bi _______ means two. binary _______ compounds are composed of two elements. See notes State the rules for writing formulas for binary compounds. See notes Be able to write chemical formulas when given a pair of elements. See notes State the rules for naming binary compounds. See notes Be able to name compounds when given a chemical formula. The net charge on a compound is zero always _______. Polyatomic ion _______ _______ is a positively or negatively charged, covalently bonded group of atoms. hydrate _______ is a compound that has water chemically attached to its ions. Chemists use symbols from the _______ periodic table to write formulas for compounds. poly _______ means “many.” See pg 591 Know the Polyatomic ions. See pg 593 Know the prefixes used in naming molecules. See notes Be able to name and make compounds with the Polyatomic ions.