Sodium (Na) _
atomic # 11
atomic mass: 23

Find # of electrons and draw them onto the Bohr model.

Assuming the atom has a neutral charge, the number of electrons equals the number of protons.  The number of protons is given by the atomic number, 11, so there are eleven electrons.

From the inner "ring" to the outer "ring":

1.  The first "ring", closest to the center of the atom, can take two electrons.

2.  The second "ring", level 2, can take the next six electrons.

3.  The rest of the electrons (three) can fit on the outermost ring.

a- all cells come from pre-existing cells