Neon
The element described would be phosphorus. Phosphorus has 5 valence electrons (more than oxygen) and 15 protons (more than sodium but fewer than argon).
The element described is chlorine. It has 7 valence electrons, which is more than oxygen but fewer than neon. Chlorine has 17 protons, more than sodium but fewer than argon.
Nitrogen has one more proton than carbon with 7 protons.
The element described has more valence electrons than oxygen but fewer than neon, more protons than sodium but fewer than argon. This element is magnesium, which has 12 protons, 12 valence electrons (2 more than oxygen but 2 less than neon), and is situated between sodium and argon on the periodic table.
The element in question is magnesium. It has 12 protons (more than sodium and less than argon), 2 more valence electrons than oxygen (which has 6), and 8 fewer valence electrons than neon (which has a full valence shell with 8 electrons).
there is no such element
The element described would be phosphorus. Phosphorus has 5 valence electrons (more than oxygen) and 15 protons (more than sodium but fewer than argon).
The element described is chlorine. It has 7 valence electrons, which is more than oxygen but fewer than neon. Chlorine has 17 protons, more than sodium but fewer than argon.
Nitrogen has one more proton than carbon with 7 protons.
The element described has more valence electrons than oxygen but fewer than neon, more protons than sodium but fewer than argon. This element is magnesium, which has 12 protons, 12 valence electrons (2 more than oxygen but 2 less than neon), and is situated between sodium and argon on the periodic table.
Sulphur.
Cl Chlorine
The element in question is magnesium. It has 12 protons (more than sodium and less than argon), 2 more valence electrons than oxygen (which has 6), and 8 fewer valence electrons than neon (which has a full valence shell with 8 electrons).
The element that fits these criteria is sulfur. Sulfur has 6 valence electrons (more than oxygen with 6, fewer than neon with 8), 16 protons (more than sodium with 11, fewer than argon with 18).
The element with 10 more protons than sulfur is argon. Sulfur has 16 protons, while argon has 18 protons.
To figure out which element it is, look at the protons. The number of protons are the atomic number, which you can find on the periodic table. In this case, 8 protons is Oxygen. You also know that it's negatively charged, because there are more electrons than protons. Because there are 2 more electrons, it would have a charge of -2.
The number of protons is different.