Hey there!
Atomic number is the number of protons.
Atomic mass is the sum of protons and neutrons.
9 + 11 = 20
Your answer is B) The atomic number is 9 & the atomic mass is 20.
Hope this helps!
Answer:Observable properties are characteristics or things about materials or objects that we can describe using our five senses. Color, texture, hardness, and flexibility are all things we can determine with our senses.
Explanation:
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2:
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