An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. how many electrons does boron have

Boron has 5 electrons in an unchanged atom.

Explanation:

The question says an unchanged atom of boron .This means the atom, boron has not gone into any reaction. It still retains it neutral status.

The proton number of boron is 5 which is the same for the atomic number. The atomic mass is given as 11. The atomic mass of an element is computed as the sum of proton and neutron .

Atomic mass= proton + neutron

For an atom that is neutral the number of electron should be equal to the number of proton. The equality accounts for it neutral nature.  Since the number proton of an unchanged atom of boron is given as 5, the number of electron should be 5 . The number of neutron can be computed as   11 - 5 = 6.

Finally, the numbers can be computed as follows;

proton number or atomic number = 5

electron number = 5

number of neutron = 6

Atomic mass = 11