Question about hydroxide

[Isabel Day 1D]

Why is calcium hydroxide written as Ca(OH)2 and not just CaOH? This comes up in problem H.7

[Hiba Alnajjar_2C]

Calcium hydroxide is written as Ca(OH)2 instead of Ca(OH) because it is a neutral compound rather than a charged one (meaning all of the charges add up to 0). In order for all of the charges to add up to 0, there have to be 2 OH, as OH's charge is -1 and Ca has a charge of +2. Therefore, in order to add up to a total charge of zero, you need 2 OH- to balance out the charge of 2+ in Ca.

(If you had Ca(OH), the total charge would be +1 rather than 0).

[805394719]

Calcium has a +2 charge whereas hydroxide has a -1 charge. Because compounds are always neutral, there must be enough of both elements to cancel out the charges. This means that there should be a total of -2 charge for hydroxide to cancel out the +2 charge of calcium. Therefore, there must be 2 hydroxide atoms in this molecule, making the equation Ca(OH)2.

[Sion Hwang 4D]

If you look on the periodic table, Calcium is located on the 2nd column. This means that Ca has two valence electrons, causing it to have a positive 2 charge as an ion.
OH, hydroxide, has a negative 1 charge.

In order to balance the charge, there must be 2 OH ions for every Ca ion.

Hence, you have Ca2+ + OH- = Ca(OH)2

[Robert Tran 1B]

The calcium ion has a 2+ charge, while the hydroxide ion has a 1- charge. Since calcium hydroxide does not have a charge, we need one calcium ion and two hydroxide ions to make the molecule neutral. Thus, the formula is Ca(OH)2.

[Kylie Lim 4G]

Calcium has 2 electrons that can be delocalized which gives it a charge of +2. The charge of hydroxide is -1, so to create a molecule with no overall charge you would need two hydroxide Ca(OH)2.