Making Measurements: ● go one sig fig past the line it tells you Precision vs Accuracy: ° ● Precision- how close together a set if measurements are ° ● Accuracy- how close the measurements is to the actual result Significant figures- ° ● represent precision of measurement ° ● Leading zeros (0.015) equals 2 sig figs ° ● Captive zeros (Chem 101) equals three sig figs ° ● Trailing zeros (150 equals two sig figs vs. 150. Equals three sig figs vs. 150.0 equals four sig figs) ° ● Exact numbers (not measurements) for example 333 students or 12 apples Atomic Symbols-
The aum- the atomic mass unit 1 amu -> 1.66 x10^-24gMass of porton = about 1 amu Mass of neutron = about 1 amu Mass of electron < 1 amu Mass in periodic table is average corrected for relative abundances of each isotope What is atomic mass is the mass of an average element with the presence of some isotopes presentPercentage times particular mass plus another percentage times the particular mass etc. Cation is a chemical species with a (+) charge - (more p+ than e-) Anion is a chemical species with a (-) charge - (more e- than p+) Chemical Formulas How many atoms of what kind are in a molecule H2O has two hydrogen and 1 oxygenCO2 has 1 carbon and 2 oxygen (CO)6 has 6 carbon and 6 oxygen Naming Chemical Compounds Ionic compounds - metal with a nonmetal; electrons are transferred from one atom to another and electrostatic attraction holds compounds togetherCovalent compounds - nonmetal with a nonmetal; electrons spend more time between atoms and proton electron attraction holds atoms togetherOrganic compounds - carbon containing compounds (excluding carbon oxides)Acids/Bases - species that donates or accepts protons (one definition)Compounds with common names - water (H2O) and ammonia (NH3) Naming Ionic Compounds Ionic compounds typically form when a metal and a nonmetal reactMetals tend to lose electrons to form positive ions and become a cationNonmetal tend to gain electrons to form a negative
ions and become an anionSymbol for the metal given first in the formula, the nonmetal comes second (cation first, anion second)Formula for binary ionic compounds (two elements present) represents the minimum number of each ion that when combined will provide equal numbers of positive and negative electrical charges (a neutral compound) Example: aluminum and oxygenAl isa group 3A metal: likely to lose 3 electrons: Al3+ Oxygen is a 6A nonmetal: likely to gain 2 electrons: O2- Answer: Al2O3 Naming Binary Ionic Compounds 1.) Cation named first and anion second2.) Cation takes the first name of the parent element3.) Anion named by taking the root name of the element and adding -ide 4.) No prefixes are used Examples:KCl- potassium chloride MgBr2- magnesium bromide CaO- calcium oxide Compounds with more than one oxidation state ° ● Transition metal
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