the answer is d because an atom is the smallest unit of a substance
Answer:
Explanation:
Ionic bonds are formed by transfer of electrons between metal and non metals. Electronic configuration of calcium: Calcium atom will lose two electron to gain noble gas configuration and form calcium cation with +2 charge.
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1 whole wave is 1 crest and 1 trough.
20 crests and 20 troughs is 20 whole waves.
20 waves / 0.4 seconds = 50 waves per second.
Frequency = 50 Hz