Question

atom a
nuclear symbol\tsubatomic particles
\t\tprotons: 18
\t\tneutrons: 18
\t\telectrons: 18
to which element does atom a belong?
atom b
nuclear symbol\tsubatomic particles
\t\tprotons: 18
\t\tneutrons: 20
\t\telectrons: 18
to which element does atom b belong?
are atoms a and b isotopes of the same element?

Explanation:

For Atom A:

Step1: Recall element identification rule

The atomic number (number of protons) determines the element. Atom A has 18 protons.

Step2: Identify element with Z=18

The element with atomic number 18 is Argon (Ar).

Step1: Use atomic number rule

Atom B has 18 protons (atomic number = 18).

Step2: Determine element

Atomic number 18 corresponds to Argon (Ar).

Step1: Recall isotope definition

Isotopes have same atomic number (protons) but different mass number (protons + neutrons).

Step2: Compare A and B

Atom A: protons = 18, neutrons = 18; Atom B: protons = 18, neutrons = 20. Same protons, different neutrons.

Answer:

Argon (Ar)

For Atom B: