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Leaving cert Chem
1 - The Atom
Question | Answer |
---|---|
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. |