Chemistry Midterm Study Guide

Topics: Atom, Electron, Chemical bond Pages: 4 (950 words) Published: November 12, 2012
Prefixdivide by
Kilo- 1,000
1 kcal = 1000 cal
1 Cal= 1 kcal
1 cal = 4.1841,000,000

Neutral atoms contain the same number of electrons and protons. •Components of a mixture can be separated (purified) by physical means. •Physical changes alter a substance without any changes to the chemical composition. •Chemical change involves breaking down a substance into other substances. •Chemical bonds are broken and reformed

Group 1 – alkali metals (light blue)
Group 2 – alkaline earth metals (yellow)
Group 17 – halogens (pale yellow)
Group 18 – noble gases (green)
Groups 1,2, 13-18 are the “Main Group” elements
Groups 3-12 are the transition metals (purple)
Left Side of PT table loses electrons, right side gains them. •Covalent bonds formed between different elements are polar. •In a molecule with covalent bonding, atoms are held together by sharing electrons. •Electronegativity (EN) measures the tendency of an atom to attract electrons (increases as you move to the right) •Greater than 1.8 = Ionic, Between 0 and 1.8 = Polar Covalent, ~0 = Nonpolar covalent •Moles = Mole * (Number of electrons in element/ 1 mole)

Atoms = Moles * 6.02*10^23, Mass number (Z) is the sum of protons plus neutrons •Isotopes of an element have the same number of protons, but different numbers of neutrons. •Isotopes of an element have the same number of protons, but different numbers of neutrons. •As bond order increases, bond length decreases. As bond order increases, bond strength increases •Allotropes: different forms of the same element

Number of electron “pairs” determines electron pair geometry: 2 linear, 3 flat triangular (trigonal planar), 4 tetrahedral •Methane CH4, Ethane CH3CH3, Propane, CH3CH2CH3 Butane. Pentane, Hexane, Heptane, Octane, Nonane, Decane

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