Magnetic resonance imaging (MRI) is a powerful diagnostic tool used in medicine. the imagers used in hospital operate at a frequency of 4.00x10^2 MHz (1MHz=10^6 Hz) calculate i) wavelength
ii) energy in joules
iii) energy in kilojoules

1)each group 16 element has how many valence electrons? ( )4 ( )6 ( )8 ( )16 2)how many dots appear in the dot structure for calcium ion, ca2+? ( )zero ( )one ( )two ( )eight 3) which of the following atoms forms a cation to obtain an octet of outer shell electrons? ( )magnesium ( )oxygen ( )fluorine ( )helium 4) an al3+ ion contains 13 protons and 10 electrons. ( )true ( )false 5) valence and non-valence electrons are represented in lewis dot structures. ( )true ( )false