Complete the table below by identifying A, B, C, D, E and F. Element Symbol Number of protons Number of neutrons Number of electrons Fluorine 9 F 19 9 A B Aluminium C D 14 13 Potassium 19 K 39 E F 19

Element Symbol Number of protons Number of neutrons Number of electrons Fluorine 9 F 19 9 A B Aluminium C D 14 13 Potassium 19 K 39 E F 19 A symbol of an element is represented as atomic number X mass number The number of protons present in the nucleus of an atom is known as the Atomic number. An electrically neutral atom has an equal number of protons and electrons. An atom is electrically neutral because the number of protons and the number of electrons present in it are the same, thus balancing the total charge of the atom. Therefore, the atomic number of aluminium atom (neutral atom) = Number of protons (D) = number of electrons = 13 Atomic mass or mass number = Number of protons + Number of neutrons Therefore, the mass number of aluminium = D + 14 = 27 Therefore, C = Al 27 13 Number of neutrons = Atomic mass or mass number - Number of protons Thus, the number of neutrons in the given fluorine atom (A) = 19 - 9 = 10 The atomic number of potassium atom (given) = 19 = Number of protons (E) = Number of electrons (given) Thus, the number of neutrons in the given potassium atom (F) = Mass number of potassium - The number of protons (E) or atomic number of potassium(given) = 39 - 19 = 20 Thus, A, B, C, D and F are given in the table as follows: Element Symbol Number of protons Number of neutrons Number of electrons Fluorine 9 F 19 9 10 9 Aluminium 13 A1 27 13 14 13 Potassium 19 K 39 19 20 19