2.1.2 Atomic structure

2.1.2 Atomic structure

1. Protons, neutrons and electrons

   • Protons and neutrons are found in the nucleus, centre of the atom
   • Electrons orbit the nucleus in shells
   • Nucleus is tiny compared to the volume of an atom
   • The nucleus is dense and accounts for almost all the atoms mass
   • The atom mostly consists of empty space between nucleus and e- shells

2. Protons have a + charge and electrons have a - charge

3. A neutral atom has the same n. of protons and electrons so is electrical neutral

4. Proton has virtually the same mass as a neutron

5. Protons and neutrons make up almost all the atoms mass

6. Isotopes

   • Isotopes of the same element have:
     • Different masses
     • Same n. of protons and e-
     • Different n. of neutrons in the nucleus
   • Isotopes are atoms of the same element with a different n. of neutrons

7. Atomic number: number of protons in the nucleus

8. Mass number: number of protons and neutrons in the nucleus

9. Isotopes of Carbon

   • Carbon exists as a mixture of isotopes, C-12, C-13 and C-14
   • The atomic n. of each isotope is 6 as each isotope has 6 protons
   • The overall charge must be 0 so each isotope also has 6 e-
   • The mass numbers are different due to different n. of neutrons
     • Carbon-12 = 12
     • Carbon-13 = 13
     • Carbon-14 = 14

10. Reactions of isotopes

    • Different isotopes of the same element react in the same way because:
      • Chemical reactions inlvolve e- and isotopes have the same n. and arrangement of e-
      • Neutrons make no difference to chemical reactivity

11. Atomic structure of ions:

    • Many atoms react by losing or gaining e- to form charge particles called ions
    • Ions are charged due to unbalanced protons and electrons