Chemistry - atomic structure

Question 1

plum pudding model

Answer 1

sphere of positive charge with negatively charged electrons dotted around within the sphere at random

Question 2

gold foil experiment

Answer 2

• by Rutherford, Geiger and Marsden
• disproved plum pudding model
• positively charged alpha particle models fired at very thin gold sheet
• if plum pudding model was correct, alpha particles would pass straight through foil, however, most of the particles passed straight through, a small number deflected, some changed direction slightly and even smaller proportion reflected straight back
• small, concentrated positive charge which caused deflection of small proportion of alpha particles

Question 3

nucleus in current nuclear model

Answer 3

• contains protons and neutrons
• found in central nucleus
• overall positively charged
• very small

Question 4

electrons in current nuclear model

Answer 4

• negatively charged
• arranged in shells around nucleus
• each shell of electrons around nucleus
• lowest energy levels filled first, 2882, atoms with full shell of electrons such as group 8 noble gases are more stable
• partially filled shells make atom reactive

Question 5

protons in current nuclear model

Answer 5

• positively charged
• in central nucleus
• no of protons = no of electrons

Question 6

mass number

Answer 6

number of protons + neutrons

Question 7

atomic number

Answer 7

number of protons

Question 8

isotopes

Answer 8

same number of protons
different number of neutrons
same chemical properties but different relative atomic mass