Inside the Atom: Quiz

Inside the Atom: Quiz

7 questions

1. Question 1EasyWhich particle has no electric charge?

   AProtonBNeutronCElectronDNucleus
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   Answer: Neutron

   Neutrons are neutral (charge 0). Protons are +1 and electrons are −1. The nucleus has an overall positive charge because it contains protons.

2. Question 2EasyThe atomic number of an element is the number of…

   Aneutrons in the nucleusBprotons in the nucleusCprotons plus neutronsDelectrons in an ion
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   Answer: protons in the nucleus

   The atomic number (Z) counts protons and identifies the element. Protons plus neutrons is the mass number.

3. Question 3EasyHow many neutrons are in an atom of $\ce{^{23}_{11}Na}$?

   A11B12C23D34
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   Answer: 12

   Neutrons = A − Z = 23 − 11 = 12. The answer 34 adds instead of subtracting.

4. Question 4MediumHow many electrons are in a calcium ion, $\ce{Ca^{2+}}$? (Ca: Z = 20)

   A18B20C22D40
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   Answer: 18

   A 2+ charge means two electrons have been lost: 20 − 2 = 18. The answer 22 adds the electrons instead.

5. Question 5EasyCarbon-12 and carbon-14 are isotopes. How do their atoms differ?

   ANumber of protonsBNumber of electronsCNumber of neutronsDCharge of the nucleus
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   Answer: Number of neutrons

   Both have 6 protons (so both are carbon) and, as neutral atoms, 6 electrons. Carbon-12 has 6 neutrons and carbon-14 has 8.

6. Question 6MediumA particle has 17 protons, 20 neutrons and 18 electrons. Which symbol represents it?

   A$\ce{^{37}_{17}Cl-}$B$\ce{^{37}_{17}Cl+}$C$\ce{^{20}_{17}Cl-}$D$\ce{^{37}_{20}Ca-}$
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   Answer: $\ce{^{37}_{17}Cl-}$

   17 protons makes it chlorine; mass number = 17 + 20 = 37; 18 electrons is one more than the protons, so the charge is 1−.

7. Question 7MediumUranium-235 and uranium-238 both have 92 protons. How many neutrons does uranium-238 have?

   A92B143C146D238
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   Answer: 146

   Neutrons = 238 − 92 = 146. Uranium-235 has 235 − 92 = 143 neutrons.