Atomic number, mass number and isotopesIB MYP Chemistry: Mind map

Exam questions on Atomic number, mass number and isotopes

1. A student is studying sodium, which is written in notation as $^{23}_{11}\mathrm{Na}$. She is learning what the two numbers in the notation tell her about the particles inside a sodium atom.
   Explain why a neutral sodium atom has 11 electrons.2 marks
2. Chemists describe atoms by the numbers of particles they contain. Four atoms are described below. Atom W has 17 protons, 18 neutrons and 17 electrons. Atom X has 18 protons, 18 neutrons and 18 electrons. Atom Y has 17 protons, 20 neutrons and 17 electrons. Atom Z has 19 protons, 20 neutrons and 19 electrons.
   Explain why atoms W and Y are the same element but have different masses.2 marks
3. Chlorine has atomic number 17. A typical sample of chlorine contains two isotopes, $^{35}\mathrm{Cl}$ and $^{37}\mathrm{Cl}$. In the sample, 75% of the atoms are $^{35}\mathrm{Cl}$ and 25% of the atoms are $^{37}\mathrm{Cl}$.
   State the number of protons, neutrons and electrons in a neutral atom of $^{37}\mathrm{Cl}$.3 marks