A molecule has four bonded atoms around a central atom. The central atom does not have any lone pairs of electrons. An example is CCl4, here the central C atom has 4 valence electrons, and the C makes a covalent bond with each of the four Cl atoms. In a C-Cl covalent bond an electron pair is shared. After fur C-Cl bonds C is left with no valence electron, hence there are no lone pair of electrons on C. Each of the four C-Cl bonds is directed towards the four corners of a tetrahedron.
Tetrahedral. like methan ch4 it doesn t have lone pairs of electrons and the bonds are oriented with a 109* 28' angle and a tetrahedron has the angles of 109 degrees so almost the same.
Mg(OH)2 is the correct chemical formula because it takes two Hydroxide ions to bond with Magnesium normally it would be written with a subscript number 2 rather than the parenthesis and number 2
