The correct answer is option A) Ca(OH)2.

Calcium hydroxide is an inorganic compound that consists of one calcium ion (Ca2+) and two hydroxide ions (OH-). It is commonly known as slaked lime or hydrated lime. The chemical formula Ca(OH)2 represents the combination of these ions in the compound.

Here is a detailed explanation of the chemical formula for calcium hydroxide:

1. Calcium ion (Ca2+):
- Calcium is a metal that belongs to the alkaline earth metal group in the periodic table.
- It has an atomic number of 20, which means it has 20 protons and 20 electrons.
- In its neutral state, it has a 2+ charge, as it loses two electrons to achieve a stable electron configuration.

2. Hydroxide ion (OH-):
- Hydroxide is a polyatomic ion that consists of one oxygen atom (O) and one hydrogen atom (H).
- It carries a 1- charge due to the extra electron from oxygen.
- Hydroxide ions are highly basic and are often involved in acid-base reactions.

3. Combination of calcium and hydroxide ions:
- In calcium hydroxide, one calcium ion (Ca2+) combines with two hydroxide ions (OH-) to form a stable compound.
- The calcium ion has a 2+ charge, while each hydroxide ion has a 1- charge. To achieve electrical neutrality, two hydroxide ions are needed for every calcium ion.

4. Chemical formula:
- The chemical formula Ca(OH)2 represents the combination of one calcium ion and two hydroxide ions.
- The subscript 2 after the OH indicates that there are two hydroxide ions in the compound.
- The parentheses are used to group the hydroxide ions together and indicate that they are bonded to the calcium ion.

In summary, the chemical formula for calcium hydroxide is Ca(OH)2, which represents the combination of one calcium ion and two hydroxide ions.