Video Transcript
Which statement about the elements in group one is incorrect? (A) Sodium has a higher melting point than potassium. (B) Potassium is less dense than rubidium. (C) Cesium is softer than lithium. (D) Rubidium is more reactive than potassium. Or (E) lithium is more reactive than sodium.
For this question, we want to know which statement about group one elements is incorrect. So what exactly are the group one elements? These elements are composed of lithium, sodium, potassium, rubidium, cesium, and francium. They are called group one elements because they are in the first vertical column of the periodic table. These elements are also referred to as alkali metals, and alkali metals have many uses. For example, lithium is used in batteries, sodium is found in salt, potassium is used by the body for contractions of our muscles, and rubidium and cesium are both used in the production of atomic clocks.
At the bottom of group one, we find francium, one of the rarest of all elements, with less than 30 grams on planet Earth. Alkali metals that have a high mass number are typically softer and denser. Rubidium has a higher mass number than potassium, so it is likely that potassium is less dense than rubidium. Therefore, option (B) is a true statement. However, we are looking for the incorrect statement. So option (B) cannot be the answer to this question. Cesium has a higher mass number than lithium. Therefore, it’s most likely that cesium is softer than lithium. Thus, option (C) is also incorrect.
Additionally, as the mass number increases, so does the reactivity of the metal due in part to the increased distance of the valence electron from the nucleus of the atom. This means that francium is the most reactive and rubidium is more reactive than potassium. Thus, option (D) is incorrect, and it’s most likely that sodium will be more reactive than lithium. Option (E) states that lithium is more reactive than sodium. Option (E) is incorrect. Thus, it must be the answer to this question.
Therefore, the statement about the elements in group one that is incorrect is (E). Lithium is more reactive than sodium.
