How many valence electrons does strontium (Sr) have? 1 2 5 6
The correct answer and explanation is:
The correct answer is 2.
Strontium (Sr) is an element in Group 2 of the periodic table, which is also known as the alkaline earth metals group. The elements in this group have two valence electrons. Valence electrons are the electrons found in the outermost shell of an atom. These electrons play a key role in chemical bonding and reactivity.
Strontium has the atomic number 38, meaning it has 38 electrons arranged in its electron shells. The electron configuration of strontium is:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s21s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 4s^2 \, 3d^{10} \, 4p^6 \, 5s^2
The outermost shell is the 5th shell, which contains the electrons in the 5s subshell. In strontium, this shell has two electrons, so the valence electrons are the two 5s electrons. These two electrons are relatively loosely held compared to inner shell electrons, which is why strontium often loses these two electrons when it forms ionic compounds, resulting in a Sr²⁺ ion.
The number of valence electrons determines many properties of an element, such as how it bonds with other elements. Since strontium has two valence electrons, it tends to form ionic bonds by losing these two electrons and achieving a stable electron configuration similar to the nearest noble gas, krypton. This characteristic is common among alkaline earth metals and is important in predicting the chemical behavior of strontium in reactions.
In summary, strontium has 2 valence electrons because it is in Group 2 of the periodic table, and its outermost shell contains two electrons in the 5s orbital. These valence electrons are critical for strontium’s chemical properties and its typical +2 oxidation state in compounds.