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A student says that the easiest way to convert a neutral sodium atom to a \(\mathrm{Na}^{+}\) cation is to add a proton to its nucleus. She reasons that this is \(\mathrm{so}\) because protons have a \(1+\) charge. What is wrong with her argument? What does a neutral Na atom become when a proton is added to its nucleus?

The mass number of a neutral atom is 19 , and its atomic number is 9 . The atom contains how many protons, electrons, and neutrons?

The mass number of a \(2+\) cation is 56 , and its atomic number is 26 . The ion contains how many protons, electrons, and neutrons?

Mendeleev arranged the elements by atomic mass and then separated them into various groups. What was his criterion for which elements were grouped together?

Scandium (Sc) is a metal that tends to lose three electrons. Copper (Cu) and zinc \((Z n)\) are also metals that tend to lose one and two electrons, respectively. Knowing this, explain why the first group in the transition metals is numbered IIIB, whereas the last two groups in the transition series are numbered IB and IIB, respectively.

How many electrons are there in \(\mathrm{Zr}^{4+}\) ? What \(2+\) cation has the same number of electrons as \(\mathrm{Zr}^{4+} ?\)

How many electrons are there in Br'? What \(1+\) cation has the same number of electrons as Br"?

What is the identity of element \(X\) if its \(2+\) cation contains ten electrons?

Magnesium has a higher first ionization energy than sodium, consistent with the periodic trend for first ionization energies. Postulate a reason why Mg has the higher first ionization energy.

Explain the major difference between Thomson's model of the atom and Rutherford's model. Draw a picture of each model.