Molecular shape is the shape of a
molecule. It depends on how
bonds are arranged in a
molecule. The major factor that influences molecular shape is the
VSEPR theory which says that in a small
molecule the
electrons will stay as far away from each other as possible.
There are five main molecular structures: Linear, trigonal planer, tetrahedral, pyrmidal, and bent.
In a linear molecule atoms are arranged in a straight line, they usually have two or three atoms. They have 180 degree bond angles, the angle they form o-o-o is a stright line which is 180 degrees.
Trigonal planers are flat triangles, as its name implies. Generally they have a central atom bonded to three other atoms. The bond angle is 120 degrees. It also has no unshared pairs of electrons.
Tetrahedral molecules are those with four surfaces. They have one central atom bonded to four others. Its bond angle is 109.5 degrees because of its 3D shape.
Pyrmidal molecules are three dimensional tripod-like structures with three atoms bonded to a central atom. They have an unshared pair that prevents them from being a trigonal planer shape.
Lastly, bent molecules, such as water, are basically bent versions of the linear form. They are bent because of an unshared pair.
Also, when one atom attempts to bond with another the orbitals of its electrons may be changed. This is known as hybrid orbitals. SP obitals are linear, SP(2) are trigonal planer and SP(3) are tetrahedral, pyramidal, or bent.
Electronegativity and polarity also play a role in the shape but only in larger molecules, with smaller it is visa-versa.