What do Magnesium and Barium have in common?
A) They have the same number of electron shells
B) They have the same number of protons
C) They have the same number of valence electrons
D) They have the same atomic mass
The correct answer and explanation is:
The correct answer is C) They have the same number of valence electrons.
Magnesium (Mg) and Barium (Ba) are both alkaline earth metals, meaning they belong to Group 2 of the periodic table. Elements in the same group share similar chemical properties due to their similar electron configurations, especially their number of valence electrons.
Valence electrons are the electrons found in the outermost electron shell of an atom, and they are crucial for determining how an element reacts with other substances. Both magnesium and barium have two valence electrons. This is because magnesium has an atomic number of 12, with its electron configuration being 1s² 2s² 2p⁶ 3s², while barium has an atomic number of 56, with its electron configuration being 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4d¹⁰ 5s².
Although they both have two valence electrons, the number of electron shells (energy levels) increases as we move down the group. Magnesium has three electron shells, whereas barium has six. This means that while their valence electrons behave similarly in terms of reactivity, the atoms themselves differ in size and energy levels.
Regarding the other options:
- A) They have the same number of electron shells: This is incorrect because magnesium has three electron shells, while barium has six.
- B) They have the same number of protons: This is incorrect because magnesium has 12 protons and barium has 56 protons, so they are different elements.
- D) They have the same atomic mass: This is incorrect because magnesium has an atomic mass of approximately 24.305 u, while barium has an atomic mass of approximately 137.33 u.
Thus, the correct characteristic they share is the number of valence electrons.