Complete the sentence indicating the number of protons and electrons in the given ion. Match the numbers to appropriate blanks in the sentences. The ion O has 7 protons and 8 electrons 9 10 11 16 17 18 What isotope has 14 protons and 15 neutrons? Enter the name of the element followed by a hyphen and the mass number (e. g., uranium- 23 4). Which element does X represent in the following expression: 2X? Enter the chemical symbol of the element.