Answer :

nkirotedoreen46

Answer:

d) 1 and 4

Explanation:

  • Elements are made up of particles known as atoms.
  • Atoms of the same element have the same properties as the element.
  • The atoms of an element may differ in terms of the number of neutrons and have a different mass number, such atoms are known as isotopes.
  • However, the isotopes have an equal number of protons or atomic number.
  • In this case, atom 1 has a mass number of 20 and an atomic number of 10 while atom 4 has a mass number of 21 and an atomic number of 21.
  • Therefore, atom 1 and 4 are isotopes of element E.

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