I think its 2-, it gained 2 electrons.
Answer:
-Atoms are neutral; they contain the same number of protons as electrons. By definition, an ion is an electrically charged particle produced by either removing electrons from a neutral atom to give a positive ion or adding electrons to a neutral atom to give a negative ion.
-An atom has an equal number of protons and electrons. An ion has an imbalance between the number of protons and electrons.
-An atom has no electrical charge. Ions have an electrical charge because they have an imbalance of protons and electrons.
Explanation:
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Answer:
Two moles of hydrogen gas combine with one mole of oxygen gas to produce two moles of water.

Explanation:
This is the required amount of each element to synthesize water. The equation has been balanced using coefficients.
There is this thing called isotopes
it means that atoms of the same element can have a different number of neutrons.
if there is a change in the no. of neutrons, there will definitely be a change in the mass number.
so the answer is A) mass number
1.75 (moles O2) × 6 (moles H2O) ÷ 9 (moles O2) = 1.17 (moles H2O)
You have to convert moles of O2 into moles of H2O so it's the number of moles you start with (1.75 O2) × the number of moles from the element you want (6 H20), then ÷ by the number of moles that the element that you already have (9 O2).