Chapter 2 lecture notes
Chapter 2 lecture notes CHMY 121N - 10
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This 6 page Class Notes was uploaded by Shania Notetaker on Tuesday September 29, 2015. The Class Notes belongs to CHMY 121N - 10 at University of Montana taught by Daniel J. Dwyer (P) in Fall 2015. Since its upload, it has received 28 views. For similar materials see Intro to General Chemistry in Chemistry at University of Montana.
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Date Created: 09/29/15
Chem 121 Notes for chapter 2 How do Scientists Classify Matter introducing atoms Pure substance a macroscopic sample consisting of only one kind of matter made up entirely of one kind of particle Mixture consist of two or more pure substances mixed together Mixtures are in two forms Homogeneous a sample that has uniform appearance and composition throughout It all looks the same Ex copper Heterogenous a sample thats not uniform throughout They can have different phases present not all the time but it can ex oil and water carbonated water Is the contents of the jar ofjam a mixture or a pure substance heterogeneous If a mixture homogeneous or heterogeneous mixture Substances and mixtures physical properties of mixtures rely on its components Pure water has a constant boiling point which is a physical property The boiling point of a mixture solution changes as the composition of the mixture changes Homogenous matter may be either a pure substance or a mixture ex water and ethanol look the same as pure ethanol or pure water Separation of mixtures Distillation separation of a mixture by heating a liquid solution until one component boils changing into the gaseous state The pure substance in the gaseous state is then collected and cooled Boiling point is a physical property Laboratory distillation apparatus Gravity ltration Elements and compounds Element pure substance that cannot be decomposed into other pure substances by ordinary chemical mean Ex silver Atom smallest particle of an element that can combine with atoms of other elements to form chemical compounds Compound pure substance that can be broken down into two or more other pure substances by a chemical change You can combine them to make bigger compound Ex water sugar 88 elements occur in nature name of an element is always a single word iron copper sulfur gold 11 elements occur in nature as gases 2 occur as liquids at room temp and pressure mercury and bromine Some elements exists as molecules rather than individual atoms Diatomics are combined atoms pure elements that like to bond together di2 Need to know Polyatomic sulfur S8 phosphorus P4 List of common elements you should know know their symbol and how to spell them start to learn them and which ones are diatomic Classi cation of matter Pure substance yes or no does it contain more than one type of atom If yes what is the number of atoms Only 1 then its an element if its 2 or more its a compound If its a mixture which most things in the world are then ask if its chunky If it is then its heterogenous if no then its homogenous What is gatorade homogeneous Baking soda compound pure substance Chlorine gas element diatomic Something must store the properties of matter thus there must be an indivisible piece of matter responsible for these properties John Dalton father of atomic theory Law of de nite composition the percentage by mass of the elements in a compound is always the same Law of conservation of mass in a chemical change mass in conserved It doesn t go away Law of multiple proportions when two elements combine to form more than one compound the different masses of one element that mobile with the same mass of the other element are in a simple ratio of whole numbers Dalton s atomic hypothesis some substances named elements are composed of one type of atom Atoms are unchanged been in the most violent chemical change Atoms of an element are identical atoms of different elements are different form one another Atoms can combine IF atom of different elements combine the substance is called compound What are atoms made of JJ Thomson Experiment devoured the electron negatively charged nearly masses particle cathode rays rst subatomic particle discovered the atom Thompson39s plum pudding model an atom is a pudding of positive charge with negatively charged plums Rutherford scattering experiment discovered the nucleus of an atom atoms are built from protons electrons and neutrons all of the positively charged and neutral subatomic particles and most the masses of that o The mostly empty space portion of the atoms about 100000 time the diameter of the nucleus Tiny negative charged subatomic particles exist in the mostly empty space and balance the post charge The whole thing is electrically neutral Charge behaviors Like charges reply Unlike charges attract The atomic nucleus Protons and neutrons are packed into a HIGH density nucleus Protons and neutron are collectively called nucleons The electron cloud electrons move through space Atomic mass units Masses of atoms and subatomic particles are so small that they are often expressed on a relative sale 1amu 112 the mass of a carbon 12 atom 16605 x 10 quot 24 often called a dalton Atom type determined by number of protons in uncles number of protein atomic number Isotopes Every atom of any particular element has the same number of protons The number of protein is an atomic of an element is the number all atoms of any particular element are not identical some have more or less mass than others Since the number roof portions and elections in a neutral atom of an element are xed there must be variation in the number of neutrons that causes this difference in mass atoms of the same element that have different masses different numbers of neutrons are called isotopes An isotope misidenti ed by its MASS NUMBER A Mass number total umber of proton neutrons Mass number of pros of neutrons Elemental name mass number What is the name of the carbon atom with 6 protons and 6 neutrons Mass number 66 12 so the same is carbon12 What is the name of the carbon isotope with 8 neutrons mass number is 6814 so carbon14 Symbol of an isotope Knows as a nuclear symbol protonsneutrons protonsquotSY Mass numberatomic numberquot Sy Atomic mass the atomic mass of an element is the sum of the products of the fractional abundance times the mass of each naturally occurring isotope Neutral atoms When an atom is uncharged electrically neutral the number of protons equals the number of electrons Whats in a neutral nickel 6O atom protons28 electrons28 neutrons32 Not all atoms are electrically neutral A charged atom or molecule is called an ion lon charge number of Protons the number of electrons Whats the charge of an atom that has 16 protons and 18 electrons lon charge 1618 2 its a sul de ion Squot2 Cations are missing a few electrons this imparts a piste charge Anions have a few extra electrons this imparts a negative charge Hydrogen isotopes Most hydrogen atoms have a nucleus with just 1 proton About 15 of every 10000 hydrogen atoms has a neutron as well hydrogen 2 The periodic Table When elements are arranged according to their atomic masses certain properties repeat at periodic intervals Periodic table of the elements a table that arrange the elements in order of increasing atomic number Nature of light No mass Some invisible light we can feel Light is emitted from an energy source electromagnetic spectrum Each element has its own discrete emission and absorption spectrum Quantum Mechanica Model Electron is a standing wave described by the wave function which has four integers Electron Con guration The number of electrons in each shell is 2nquot2 A list of the number of electrons in each energy level in an atom The principal energy level and sub level specify the energy level of an electron Two principles are used 1 at ground state the electrons ll the lowest energy orbitals available 2 no orbital can have more than two electrons
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