27 . Which atom has an ionic radius that is larger than its atomic radius?
(A) Na
(B) K
(C) Mg
(D) Ca
(E) Cl
28 . The basic structure of crystalline substances is called
(A) unit cell
(B) molecule
(C) lattice
(D) geode
(E) matrix
29 . The oxidation state of nitrogen is most negative in which of the following compounds?
(A) N 2
(B) N 2 O
(C) NH 3
(D) NO 2
(E) NO 3
30 . An insulated tube with a movable piston at one end had 500 J of heat added to it. If,
during the experiment, the piston moves and does 75 J of work on the atmosphere, what
is the change in energy of the tube system?
(A) 575 J
(B) 500 J
(C) 425 J
(D) –75 J
(E) –425 J