Boron has 5 protons.

In chemistry, the atomic number of an element is defined as the number of protons in the nucleus of each atom of that element. For boron, the atomic number is given as 5, so every boron atom—charged or uncharged—contains 5 protons in its nucleus.

Because the atom in your question is uncharged (neutral), it also has 5 electrons to balance the 5 positively charged protons, though that is extra information beyond what you asked.

So, an uncharged atom of boron with atomic number 5 and atomic mass 11 has 5 protons.

TL;DR: Number of protons in boron = its atomic number = 5.

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