Hydrogen has 1 valence electron, whereas helium has 2 valence electrons.
Gallium is a mono-atomic metal element. So their atoms are atoms, and as many as you have!
8 valence electrons
In the compound Al₂O₃, there are two aluminum (Al) atoms and three oxygen (O) atoms. Aluminum has 3 valence electrons, so 2 Al atoms contribute a total of 6 valence electrons. Oxygen has 6 valence electrons, so 3 O atoms contribute 18 valence electrons. Therefore, the total number of valence electrons in Al₂O₃ is 6 + 18 = 24 valence electrons.
H2O2 is a compound, and the concept of "valence electrons" applies to atoms but not to compounds. If the question is or should be intended to be, "How many valence electrons did the atoms in one formula unit of H2O2 have before they reacted to form the compound?", the answer is one from each hydrogen atoms and six from each oxygen atom, for a total of 14.
There are 15 electrons in phosphorus, 45 electrons from five fluorine atoms, and they make 60 electrons altogether.
Most second period atoms have four valence electrons when they combine with other atoms to form molecules.
Oxygen atoms have 6 valence electrons, while sulfur atoms have 6 valence electrons as well.
Oxygen has six valence electrons.
Gallium is a mono-atomic metal element. So their atoms are atoms, and as many as you have!
Aluminum has 3 valence electrons.
8 valence electrons
3
Four.
carbon has 4 valence electrons and can form a maximum 4 bonds with other atoms.
Serine has five valence electrons. It has three valence electrons from the oxygen atom and one valence electron each from the carbon and nitrogen atoms in its structure.
The first two elements in the 2nd period are metals, and form ionic compounds rather than molecules. Boron, carbon, nitrogen, oxygen, and fluorine share electrons, forming covalent bonds with other nonmetals so that they will each have a full valence shell with eight electrons. The noble gas neon already has eight valence electrons and is generally nonreactive.
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