BSC 2010 BIOLOGICAL SCIENCE I SPRING 2012 STUDY GUIDE 1 THE CHEMICAL CONTEXT OF LIFE Vocabulary Atom Building blocks of elements anion negative charge chlorine attracts to the cation Sodium NaCl smallest unit of matter that still retains the properties of an element atomic mass atomic number the sum of the protons and neutrons in the nucleus number of protons in its nucleus For uncharged atoms this is also the number of electrons TOP of square in periodic table Cation Attracts to the anion Chlorine NaCl Positive charge Sodium chemical reaction reactants and products Are the amking and breaking of chemical bonds In a chemical reaction reactants interact to form products 2 H2 1O2 2H2O The coefficients of reactants and products are such that the total number of individual atoms is the same in the reactants and products Matter is conserved in chemical reactions chemical bonding atoms with incomplete calence shells can share or transfer valence electrons with other atoms These interactions usually result in atoms staying close together held by attractions called chemical bonds compound Joining elements together consists of two or more elements in fixed ratios Characteristics of compound are different than the joining elements covalent bonds non polar and polar type of chemical bond Is the sharing of a pair of valence electrons by two atoms In a covalent bond the shared electrons count as a part of each atom s valence shell There is an equal sharing of electrons between the two identical H atoms This is called a non polar covalent bond Oxygen atoms have 6 electrons in their outer shell 2 of which are unpaired o this explains why a molecule of oxygen consists of two atoms of oxygen held together by two non polar covalent bonds a double bond Water is formed when oxygen share a pair of electrons with each of two different atoms of hydrogen But oxygen attracts electrons more strongly than hydrogen it is more electronegative and the electrons spend more time closer to the oxygen o Partial negative on oxygen partial positive on hyrogen o This is a polar covalent bond dalton electron negative charge Primarily responsible for interactions between atoms during the formation of compounds and other chemical reactions Electrons have differing amounts of potential energy Energy is the capacity to do work of to cause change The further away the electron is from the nucleus the higher the energy it has More attractive to electrons electron orbital electro negative element energy shell Fundamental building blocks of matter can t break them down into other substances Atomic number defines the element an electrons state of potential energy has to do with its energy and that location is called the energy shell First shell is the lowest energy level 2nd is the higher energy level 3rd shell is the highest energy level hydrogen bonds type of chemical bond weaker than ionic and covalent bond forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom in living cells the electronegative partners are usually oxygen and or nitrogen atoms important because it can be broken hydrogen bond between water and ammonia NH3 inert gasses ionic bonds type of chemical bond stealing of electron Sodium Chloride NaCl outer shell isotope o Easier for sodium to be happy to get rid of its 1 valence and give it to Chlorine to fill its different atoms of an element with the same number of protons but a different number of neutrons and atomic mass Isotopes are the same element and have the same chemical properties but may have different physical properties matter A molescules or compounds molecular weight is the simple sum of the atomic mass of all of the Anything that takes up space and has mass molecular weight constituent atoms MW of NaCl 22 99 35 49 MW Gives types and numbers of atoms in a molecule molecular formula o H2O moles and molar solutions Mole molecules o A measure of the number of molecules of a given type where 1 mole 6 x 1023 o If you measure out an amount of substance in grams equal to the molecular weight you will always have 6 x 1023 molecules or 1 mole Molar solutions o Nucleus neutron Protons and neutrons no electrical charge periodic table potential energy stored energy that matter has because if its location or structure the two ends sides top and bottom are different from one another Human beings are polar because how head is different from our feet polarity proton positive charge radioactive valence shell electrons and number outer shell is valence shell Electrons in outer shell are called valence electrons and the number of unpaired valence electrons is the valence number Valence number of carbon is 4 Valence number of fluorine is 1 An atom wants to pair up electrons to fill up the outer shell Depends on the valence number how many left it needs van der Waals interactions Even in charged atoms or compounds with non polar bonds electrons can be distributed asymmetrically resulting in regions with very slight positive and negative charges Weaker than ionic but strength in numbers Theyre attractions between molecules that are close together as a result of complimentary asymmetric charge distributions Interactions can be strons as between molecules of a geckos toe hairs and a wall outer shell rule Syrucural formula outer shell wants to be full stable Noble gasses are the happiest outer shell is full helium neon argon H O H O O Gives types and number of atoms in molecule But in addition illustrates how atoms are arranged and bonded with each other Bond strengths Covelent Ionic in water Hydrogen Van der Waals Ionic in solid Principles and Concepts Strength kcal mole 70 100 10 4 5 1 2 90 140 Be familiar with the elements that are important to life Table 2 1 o 25 of the 92 elements are essential to life o Oxygen carbon hydrogen nitrogen o Calcium phosphorous potassium sulfur sodium chlorine magnesium o Trace elements 0 01 Boron chromium cobalt copper fluorine iodine iron manganese MO Selenium silicon tin vanadium zinc Understand the basics of atomic structure and the nature and properties charge and mass of the subatomic particles that atoms are made of o Always found in similar organization protons and neutrons are in the center electrons are a cloud around them o Neutrons and protons have nearly identical masses o Atomic masses are expressed in terms of Daltons o Neutrons and protons have a mass of 1 dalton o Mass of an electron have an inevitable
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