An atom of an element has an atomic number of 9 and a mass number of 19:

(a) State the number of protons and neutrons in the nucleus of this atom.

  • The atomic number tells us the number of protons in the atom. For an atom with an atomic number of 9, there are 9 protons.

  • The mass number is the sum of the protons and neutrons. Therefore, the number of neutrons is the mass number minus the atomic number:

    Neutrons=Mass number−Atomic number=19−9=10 neutrons

So, this atom has 9 protons and 10 neutrons.

(b) State the number of electrons in this atom.

In a neutral atom, the number of electrons is equal to the number of protons. Therefore, this atom has 9 electrons.

(c) Show with electron cross-dot diagrams the formation of ions by this atom.

This atom has an atomic number of 9, which corresponds to fluorine (F). Fluorine has 7 valence electrons and needs one more electron to complete its octet.

  • Fluorine gains one electron to form an anion (F⁻):

    Electron dot structure:

    :F: + e⁻ → :F⁻:

(d) Write the electronic configuration of this element.

For fluorine (atomic number 9), the electronic configuration is:

1s2 2s2 2p5\text{1s}^2 \, \text{2s}^2 \, \text{2p}^5

This means fluorine has 2 electrons in the first shell and 7 electrons in the second shell.

(e) Point out its group in the periodic table.

Fluorine is in Group 17, which is the halogen group in the periodic table.

(f) Point out its period in the periodic table.

Fluorine is in Period 2 of the periodic table.

Related Questions:

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  2. Describe the ways in which bonds may be formed.
  3. Describe the formation of a covalent bond between two non-metallic elements.
  4. Explain with examples single, double, and triple covalent bonds.
  5. Find the number of valence electrons in the following atoms using the periodic table:
  6. Represent the formation of cations for the following metal atoms using electron dot structures:
  7. A sample of sulfur from a volcano was analyzed to give the following composition of isotopes (Atomic No. of S = 16):
  8. The atomic number of an element is 23, and its mass number is 56.
  9. State octet and duplet rules.
  10. Explain the formation of a covalent bond between two nitrogen atoms.
  11. How does Al form a cation?
  12. Draw an electron cross and dot structure for an H₂O molecule.
  13. Describe the importance of noble gas electronic configuration.
  14. Why is an atom electrically neutral?
  15. The atomic symbol of aluminum is written as Al. What information do you get from it?
  16. Write the valence shell electronic configuration of an element present in the 3rd period and Group IIA.
  17. Define halogens.
  18. Which atom has a higher shielding effect, Li or Na?
  19. Explain why Na has higher ionization energy than K.
  20. Alkali metals belong to the S-block in the periodic table. Why?