an atom contains 22 protons and 26 neutrons. what is its mass number?

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Nature

An atom with 22 protons is the element titanium (Ti). The number of protons, 22, is the atomic number that determines the element's identity. If this atom also contains 2 neutrons, its mass number (protons + neutrons) is 24. This would be an isotope of titanium with the symbol Ti\text{Ti}Ti and mass number 24, written as 2224Ti\mathrm{^{24}_{22}Ti}2224​Ti. To summarize:

  • Protons = 22 (Titanium)
  • Neutrons = 2
  • Atomic number = 22
  • Mass number = 24
  • Isotope symbol: 2224Ti\mathrm{^{24}_{22}Ti}2224​Ti

Titanium normally has more neutrons (e.g., the most common isotope titanium-48 has 22 protons and 26 neutrons), so an atom with only 2 neutrons would be a very unusual, very light isotope of titanium.