Protons, neutrons and electrons

Answer Key - Grade 8 Science Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   Ari reads that an iron atom has mass number 56 and 30 neutrons. How many protons does it have?

   26 protons
2. 2.

   Bo reads that a copper atom has mass number 63 and 34 neutrons. How many protons does it have?

   29 protons
3. 3.

   Esme reads that a boron atom has mass number 11 and 6 neutrons. How many protons does it have?

   5 protons
4. 4.

   Jun says electrons sit inside the nucleus, next to the protons. Agree or disagree?

   • Agree: the nucleus holds the whole atom
   • Agree: opposite charges sit together
   • Disagree: electrons are around the nucleus
   • Disagree: electrons are outside the whole atom
5. 5.

   Luz says an electron has about the same mass as a proton, since their charges balance. Agree or disagree?

   • Disagree: an electron is far lighter
   • Agree: equal charges mean equal mass
   • Agree: both are particles in one atom
   • Disagree: an electron is heavier

6. Read this first

   Table (IUPAC data)

   Atomic number, symbol, name. 5 B boron; 6 C carbon; 7 N nitrogen; 8 O oxygen.

7. 6.

   A carbon atom has 6 protons and 6 neutrons. If it had one more neutron, what would it be, Milo?

   • Nitrogen, the next element
   • Still carbon, with mass number 13
   • Boron, since it is heavier
   • Oxygen
8. 7.

   Imagine the same carbon atom with one more proton instead. Using the table, what would it be, Noah?

   • Element 13, from the mass number
   • Nitrogen
   • Still carbon, since neutrons decide
   • Boron
9. 8.

   Atomic number, symbol, name. 16 S sulfur; 17 Cl chlorine; 19 K potassium. Atom X has 17 protons and 18 neutrons. Atom Y has 17 protons and 20 neutrons. What are they, Pia?

   • Both sulfur
   • X is chlorine and Y is potassium
   • Two different elements, since neutrons differ
   • Both chlorine
10. 9.

    Ren checks three classmates' atom models. Which one is right?

    • Particles spread evenly through the atom
    • Protons and neutrons in the center, electrons around
    • Neutrons marked −, electrons marked +
    • Electrons drawn inside the nucleus
11. 10.

    A model shows a tiny nucleus and a wide cloud of electrons. Where is most of the mass, Zee?

    • Nowhere: atoms are empty
    • In the tiny nucleus
    • In the wide electron cloud
    • Shared evenly, since everything counts the same