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Leaving cert Chem

1 - The Atom

QuestionAnswer
Describe the plum pudding model. 1. The atom itself was a solid sphere of positive charge. 2. The electrons were embedded at random into this positively charged sphere.
List 3 observations gathered from Rutherford's gold foil experiment (1910). 1. Most of the alpha particles went straight through the gold foil. 2. Some particles were deflected at large angles. 3.Some of the particles reflected back along their own path.
Which scientist determined the size of the charge on an electron? Robert Millikan.
2010 Q5 State two assumptions of Daltons Atomic Theory of 1808. 1. All matter is made up of very small particles called atoms. 2. All atoms are invisible and cannot be broken down into simpler particles.
Name the scientist who measured the ratio of charge to mass of the electron (1897). J.J Thomson.
Name the scientist who proved that the electrons in an atom reside in an electron cloud surrounding a small dense positive central nucleus (1910). Ernest Rutherford.
2011 Q4 Give two properties of cathode rays. 1. They are streams of negatively charged particles called electrons. 2. They are deflected in magnetic fields.
2012 Q11 What are alpha particles? Groups of two neutrons and two protons stuck together i.e, the nucleus of the helium atom.
In Rutherford's gold foil experiment 1910 explain why some alpha particles were deflected at large angles. Because they came very close to the high concentration of positive charge in the nucleus, the positively charged alpha particles and the positively charged nucleus repelled one another.
Explain why some alpha particles were reflected back along their path. (6) Some alpha particles were reflected back along their original path when they scored a direct hit with the nucleus (3) This only happened to a few alpha particles. the positive charge in the gold foil was condensed in the nucleus. mostly empty space.
Created by: neilkelly