Question

What isotope has 17 protons and 18 neutrons? Enter the name of the element followed by a hyphen and the mass number (e.G., uranium-234)?

Answer 1

Number of protons is same as the atomic number and number of neutrons is equal to the subtraction of the atomic number from the mass number i.e.

number of neutrons  = atomic number - mass number

Now, the atomic number = $17$ = number of protons

$18 = 17 - mass number$

mass number  = $18+17$

= $35$

Thus, the element is chlorine.

Name of the element is Chlorine-35.