Mendeleev found that when he arranged the known elements according to their atomic mass, the entries in the table exhibited a pattern of chemical properties that repeated itself in groups of eight elements. This led to the generalization now known as:
A. an atomic model.
B. valance electrons.
C. the periodic table.
D. the octet rule.
D
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Its defoliant effects were first noticed when it leaked from gas lights; later found to be produced by plants themselves.
Choose the letter of the best match: A. abscisic acid B. auxin C. ethylene D. cytokinin E. gibberellin
What do gametes, spores, and the gametophyte generation have in common?
a. They are all diploid. b. They are all haploid. c. They are present in vascular plants only. d. They are all produced by meiosis. e. They are all triploid.
The protective membranes that surround the brain and spinal cord are called the
A. peritoneum. B. meninges. C. myelin sheath. D. meconium.
Eugenic laws were enacted in an attempt to
A. prevent some individuals from reproducing. B. eliminate "bad genes" from the human population. C. improve the human gene pool. D. All of these answers are true.