# chapter 5

 Dalton believed believed elements are minute, indivisible particles called atoms. Dalton believed atoms of the same element are alike in  mass and sizes Dalton believed Atoms of different elements have different masses and sizes Dalton believed chemical compounds are formed by the union of  two or more atoms of different elements. Dalton believed Atoms combine to form compounds in simple  numerical ratios (such as 1-1, or one to 2, or 2 to 3 and so on). Dalton believed two elements may combine in different ratios to form more than one compound Law of definite composition a compound always contains two or more elements in a definite proportion by mass Law of multiple proportions Atoms of two or more elements may combine in different ratios to produce more than one compound. What do the laws of multiple and definite composition state: 1) the composition of a particular substance will always be the same no matter what its origin or how it is formed. 2) the composition of different compounds formed from the same elements will always be unique. A law is a summary of observed behavior A model/theory is an attempt to explain the observed behavior. subatomic particles are electrons protons and neutrons what is the nucleus contains protons, neutrons and electons what's the atomic number number of protons isotope is valies in the loss or gain (#) of neutrons, but has the same amount of protons/atomic number. mass number is the neutrons+ protons=mass number mass of an electron compared to proton 1/1837 amu, with neg charge mass of a proton 1.673 X10^-24 g w/positive charge mass of neutron and it's charge 1/1.675X10^-24 g, with  no/neutral charge Ion is an atom that lost or gained an electron (having +/- charge). Thomson's model of atom negative electrons are embedded in positive atomic sphere. Rutherford's model of the atom atoms are composed of protons and neutrons surrounded by electrons which occupy mostly empty space. 6 parts of Dalton’s Atomic Theory 1.Elementsare composed of minute indivisible particles called atoms. 2.Atomsof the same element are alike in mass and size. 3.Atomsof different elements have different masses and sizes. 4.Chemicalcompounds are formed by the union of two or more atoms of different elements. 5.Atomscombine to form compounds in simple numerical ratios, such as one to one, twoto two, two to three, and so on. 6.Atomsof two elements may combine in different ratios to form more than one compound. Properties of electrical charges •Charge may be of two types: _______ and ______. •Unlike charges ________t (positive attracts negative), and like charges repel (negative repels negative and positive ______ positive). •Charge may be transferred from one ________ to ________, by ________ or __________. •The less the distance between two charges, the _______ the force of attraction between ______ charges (or _______ between identical charges). •Charge may be of two types:positive and negative. •Unlike charges attract (positiveattracts negative), and like charges repel (negative repels negative andpositive repels positive). •Charge may be transferred from oneobject to another, by contact or induction. •The less the distance between twocharges, the greater the force of attraction between unlike charges (orrepulsion between identical charges). Who discovered ions Faraday discovered that certainsubstances, when dissolved in water, conducted an electric current. Why did he call them ions •He found that atoms of someelements moved to the cathode (negative electrode) and some moved to the anode(positive electrode). •He concluded they were electricallycharged and called them ions (Greek wanderer). what were Rutherford's findings regarding uranium He studied the emission of rays from uranium (alpha and beta rays:•If a positive alpha particle approached close enough to the positive mass in the gold foil it was deflected. •Most of the alpha particles passed through the gold foil.  This led Rutherford to conclude that a gold atom was mostly empty space. Rutherford's contribution to understanding the atom: •atom had a dense, positively charged nucleus.•a light,negatively charged electrons were present in an atom and offset the positive nuclear charge. Chadwick’s contribution to understanding the atom: •Chadwick’swork in 1932 demonstrated the atom contains neutrons. How do these numbers relate to describing an element:  Top left, Bottom left, and element symbol. *Mass number=top left (protons+neutrons), *atomic number=bottom left/proton number, *Element symbol=proton number Authorstudysuccess ID183760 Card Setchapter 5 Descriptionchapter 5- Updated2012-11-25T05:25:31Z Show Answers