How many electrons can be in an electron shell?

There are 64 electrons in the fourth electron shell. to find this the equation is 2n^2 n being the shell number so in this case 2*4^2 = 64.

The first shell can have either one or two electrons, no more than that.2 the first shell is 1s2

An electron does not have "electron shells" at all; these are characteristic of atoms, not electrons. No electron can occupy more than one shell of an atom unless the atom is excited.

Nine electrons in two shells: 2 and 7 resp. in the 1st and 2nd. Remember: number of shells is the number (name) of the period in the periodic system.

3 shells; 2 electrons in the first shell, 8 in the second shell and 8 in the third shell.