A student conducts an investigation using mall spares. In one part of the investigation, he needs to closely examine a spore sample. Whach piece of equipment does the student need to we to keep mekl spares from entering his respiratory system?

The wave shown on the electromagnetic spectrum disturb the medium it passes through a)different frequency. b)the same frequency .

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

What four properties do all waves have in common