How many valence electrons does an atom of gallium have?
A) 1
B) 2
C) 3
D) 4
The correct answer and explanation is :
The correct answer is C) 3.
Explanation:
Valence electrons are the electrons in the outermost electron shell of an atom that participate in chemical bonding. The number of valence electrons is crucial for determining how an element reacts chemically with others.
Gallium (Ga) is a chemical element with the atomic number 31. This means that a neutral gallium atom has 31 electrons. To determine the number of valence electrons, we need to understand how these electrons are arranged in the atom’s electron shells.
The electron configuration for gallium can be written as follows:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p¹
Breaking it down:
- The 1s² 2s² 2p⁶ 3s² 3p⁶ are the inner electron shells, filling the first three energy levels.
- The 4s² 3d¹⁰ 4p¹ are the outermost shells, located in the 4th energy level.
The outermost shell, in this case, is the 4th energy level, which contains 2 electrons in the 4s orbital and 1 electron in the 4p orbital, making a total of 3 valence electrons.
Because gallium is in Group 13 of the periodic table, which is also known as the boron group, all elements in this group have 3 valence electrons. This is consistent with the electron configuration and the periodic table trend that elements in the same group tend to have similar chemical properties, particularly in their valence electron count.
These three valence electrons are what gallium can use in chemical bonding. When gallium forms compounds, it typically donates or shares these electrons in reactions, following the typical trends for metals in Group 13, such as the formation of +3 ions in ionic compounds.
Thus, gallium has 3 valence electrons, and the correct answer is C) 3.