There are 2 valence electrons
Explanation:
The number of protons in the element C^12 (Carbon) is 6, number of electrons 12 and number of Neutrons is 6, same as the number of protons it contains
C^13 has 13 electrons, 6 protons and 7 Neutrons this one's neutron number is different from proton number because it's an isotope
Na^-1 has gained an electron so the number of electrons it has = 24 and the number of protons shown as 11 which means there are 23 - 11 = 12 Neutrons
O^-2 has gained two electrons and got 18 electrons in total, 8 protons and 8 neutrons
