Regents Chemistry atomic structure and the periodic table quiz quiz

Which two particles have approximately the same mass?

What does the atomic number of an element equal?

An atom has a mass number of $31$ and an atomic number of $15$. How many neutrons does it have?

Atoms of $^{16}_{8}\text{O}$ and $^{18}_{8}\text{O}$ are isotopes because they have the same number of

An element has two isotopes: mass $24.0$ at $79\%$ and mass $26.0$ at $21\%$. Which value is the best estimate of its average atomic mass?

Which electron configuration represents an atom of phosphorus in the ground state?

An atom with the configuration $2\text{-}7\text{-}2$ is best described as

How many valence electrons does an atom of sulfur ($2\text{-}8\text{-}6$) have?

As you move from left to right across a period, the atomic radius generally

Which element has the highest electronegativity?

Which group contains the noble gases?

Compared with a sodium atom, a sodium ion ($\text{Na}^{+}$) has

From the nuclide $^{27}_{13}\text{Al}^{3+}$, how many electrons are present?

Which statement about the modern (wave-mechanical) model of the atom is correct?