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Answer the following questions related to K.
(a) In terms of atomic structure, explain why the atomic radius of K is larger than that of Na.
(b) In terms of atomic structure, explain why the first-ionization energy K is less than that of Ca.
(c) K forms the compound K2O, which is an ionic compound that is brittle. Identify another element, M, that is likely to form a brittle, ionic compound with the formula M2O. Justify your answer in terms of periodic trends.
(d) The compound K2O2 also exists. A chemist can determine the mass of K in a sample of known mass that consists of either pure K2O or pure K2O2. From this information, can the chemist answer the question of which compound is in the sample? Indicate yes or no, and explain.

Both potassium and sodium are members of group one but potassium has four shells while sodium has only three shells. This means that potassium has a larger atomic radius than sodium

Calcium has a larger size of nuclear charge compared to potassium. Due to this increase in size of the nuclear charge, calcium has a higher first ionization energy than potassium.

Another element that forms a compound of the formula M2O is sodium. This is a common property of group one elements. Elements in the same group has the same number of valence electrons and therefore form compounds of the same general formula.

From the information on the mass of K in the samples of K2O and K2O2 alone, the chemist can not indicate which compound is in the sample since the compounds will contain exactly the same mass of potassium.

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