2- In water, ratie of exygen to hydrogen by atoms is A-2:1 B- 1:2 C-8:1 D- 1:8 3- Isotopes are atoms of the same element with different numbers of A- Protons B- Electrons C- Neutrons D- Positron 4 Which of the following places the atomic subshells in the correct order of relative energy, starting with the subshell of lowest energy? A-d. p.s B-s, d, p C-sp.d D-p,s, d 5. Calcium has an atomic number of 20. What is its electronic configuration? A- Is 2s 2p B- 1s 2s 2p 3s 3p 3d C-ls 2 2p 2d 3s 3p D-1s 2s 2p 3s 3p 4s 6 What is the chemical symbol for magnesium? A- Ma B- Mn C-M D- Mg 7- An atom of sodium (Na) has an atomic number of 11 and a mass number of 23, Which of the following statements is correct? A-An atom of sodium has 1I protons, 11 electrons, and11 neutrons. B- An atom of sodium has 11 protons, 12 electrons, and 11 neutrons. C An atom of sodium has 11 protons, I1 electrons, and 12 ncutrons, D-An atom of sodium has 1 protons, 12 electrons, and 12 neutrons.