Question

1 the atomic number of lithium is 3. how many neutrons does an atom of lithium have if it is represented by the symbol shown below? ⁷li 2 neutrons 13 neutrons 4 neutrons 7 neutrons 2. the atomic number of fluorine is 9. how many electrons does an ion of fluorine have if it is represented by the symbol shown below? ¹⁹f¹⁻ 8 electrons 9 electrons 10 electrons 20 electrons

Explanation:

Step1: Recall neutron - mass number relation

The mass number is written as the superscript in the isotope notation. For an atom, Mass number (A)=Number of protons (Z)+Number of neutrons (N). Given the atomic number of lithium (Z = 3) and mass number A = 7 for $^{7}Li$.

Step2: Calculate number of neutrons

We use the formula N=A - Z. Substituting A = 7 and Z = 3, we get N=7 - 3=4.

Step3: Recall electron - atomic number relation for ions

For an atom, the number of electrons is equal to the atomic number. For an ion, if it has a negative charge, the number of electrons is the atomic number plus the magnitude of the charge. The atomic number of fluorine is Z = 9 and the ion is $^{19}F^{-1}$.

Step4: Calculate number of electrons in fluoride ion

Since the ion has a - 1 charge, the number of electrons E=Z + 1. Substituting Z = 9, we get E=9+1 = 10.

Answer:

1. C. 4 neutrons
2. C. 10 electrons