Which of the following statements about magnesium atoms is not correct? 1. all magnesium atoms have the same number of protons. 2. all neutral magnesium atoms have 12 protons and 12 electrons. 3. all magnesium atoms have an atomic number of 12. 4. all atoms with an atomic number of 12 are magnesium atoms. 5. all magnesium atoms have the same number of neutrons

5. All magnesium atoms have the same number of neutrons

Explanation:

Magnesium (Mg) is a chemical element. Its atomic number (Z) is 12 (number of protons in the nucleus of the Mg atom).

The Magnesium has three stable isotopes: 24Mg, 25Mg and 26Mg. All these isoforms have 12 protons in their atoms (same atomic number), however they  vary in the mass number of the atom (M).

The mass number of the atom (M) is equal to the sum of protons and neutrons in the nucleus.

Based on this information we can know how many neutrons each isotope has

24 Mg = 12 protones + 12 neutrons

25Mg = 12 protones + 13 neutrons

26Mg = 12 protones + 14 neutrons

In this way we conclude that not all magnesium atoms have the same number of neutrons

but there is no

i guess you forgot putting it.