Question

A) 3 and 4

b) 2 and 3

c) 1 and 2

d) 1 and 4

Answer 1

d) 1 and 4

Step-by-step 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.