4. Atoms and Elements

Argon’s most abundant isotope is argon-40. How many neutrons are in one atom of ${}_{40}{}^{18}\mathrm{Ar}$?

For each representation of a nucleus A through E, write the atomic symbol and identify which are isotopes. (4.4, 4.5) Proton (red) Neutron (white)a.

What is the mass number of the isotope lithium-7?

Which element has 16 protons and 16 neutrons in its nucleus?

Which isotope of platinum contains 118 neutrons? (Platinum has atomic number $78$.)

Which of the following is an isotope of lithium?

An atom has 53 protons and 74 neutrons. Which isotope is it?

Which statement best describes an isotope such as carbon-14?

Which of the following represents an isotope of lithium (Li)?

Which element is represented by an atom with 13 protons and 14 neutrons (i.e., atomic number $13$)?

An atom has 4 protons and 5 neutrons. Which element is it?

In atomic structure, how is the mass number of an atom calculated?

An atom has 38 protons and 50 neutrons. What element is it (and what isotope is specified by these numbers)?

Which isotope has 14 protons and 15 neutrons?