Fig. 6.1 shows the electron arrangement in an atom of an element. (a) Identify the element shown. [1] (b) State the electron arrangement of this atom. [1] (...
Question 1 Report
Fig. 6.1 shows the electron arrangement in an atom of an element.
(a) Identify the element shown. [1]
(b) State the electron arrangement of this atom. [1]
(c) State the mass number of this atom. [1]
(d) Calculate the number of neutrons. [1]
(e) This atom forms an ion with a charge of +1. Explain how this ion is formed and state the electron arrangement of the ion. [2]
Answer Details
(a) Identify the element [1]
Sodium (Na). [1]
The diagram shows 11 protons in the nucleus. Element number 11 on the periodic table is sodium.
(b) Electron arrangement [1]
2, 8, 1 [1]
Counting the electrons in the diagram: shell 1 (innermost) has 2 electrons, shell 2 has 8 electrons, and shell 3 (outermost) has 1 electron. Total = 11 electrons, matching the 11 protons in a neutral atom.
(c) Mass number [1]
Mass number = protons + neutrons = 11 + 12 = 23 [1]
The mass number (nucleon number) counts all particles in the nucleus.
(d) Number of neutrons [1]
Neutrons = mass number − proton number = 23 − 11 = 12 [1]
This is consistent with the "12n" label shown in the nucleus in the diagram.
(e) Ion formation and electron arrangement [2]
The atom loses one electron from its outer shell (shell 3). Losing a negative charge leaves the atom with more protons than electrons, giving it a net charge of +1. [1]
The ion has the electron arrangement 2, 8. [1]
The Na+ ion now has a full outer shell of 8 electrons (a stable octet), which is the same electron arrangement as the noble gas neon.
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