In the nucleus of an atom, there are 18 protons and 20 neutrons. what are the atomic number and mass number of this isotope



Answer :

The atomic number is the number of protons in the element - just 18. The mass number is the atomic number plus the number of neutrons: 18 + 20 = 38.

An isotope is just an element with a particular number of neutrons, which is different from the element with a different number of neutrons. Element 18 is argon, and this particular isotope would be names Argon-20, or Ar-20

The atomic number of the isotope is [tex]\boxed{18}[/tex] and the mass number of the isotope is [tex]\boxed{38}[/tex].

Further Explanation:

Given:

The number of protons is [tex]18[/tex].

The number of neutrons is [tex]20[/tex].

Concept:

The atomic number of an element defined as the number of protons present in the nucleus of the atom. The atomic number of the element defines the several chemical properties and the position of the element in the periodic table.

Therefore, the atomic number of the isotope in the given question is:

[tex]Z = {n_p}[/tex]

Here, [tex]{n_p}[/tex] is the number of protons and [tex]Z[/tex] is the atomic number.

Substitute [tex]18[/tex] for [tex]{n_p}[/tex] in above expression.

[tex]Z = 18[/tex]

Thus, the atomic number of the isotope is [tex]\boxed{18}[/tex].

The mass number of the isotope is the number of nucleons consisted by the atom. It means that the mass number of the isotope is the sum of the number of protons and neutrons present in the nucleus.

The mass number can be represented as:

[tex]A = {n_p} + {n_n}[/tex]

Here, [tex]{n_n}[/tex] is the number of neutrons and [tex]A[/tex] is the mass number of isotope.

Substitute the values of [tex]{n_p}[/tex] and [tex]{n_n}[/tex] in above expression.

[tex]\begin{aligned}A&=18+20\\&=38\\\end{aligned}[/tex]

Thus, the mass number of the isotope is [tex]\boxed{38}[/tex].

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Answer Details:

Grade: High School

Subject: Physics

Chapter: Atoms

Keywords:

Nucleus, atoms, neutrons, number of protons, atomic number, mass number, isotope, 18 protons, 20 neutrons, Z=18, A=38.