To form a major scale you must have the following pattern of tones and semitones.

Ensuring that you only have one of each note 'letter' name and two of the Tonic.

i.e.

C, D, E, F, G, A, B, C'

Tone, Tone, Semitone, Tone, Tone, Tone, Semitone

or

T, T, S, T, T, T, S