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# Question:(i) Write the electronic configurations of the following ions: (a) H– (b) Na+ (c) O2– (d) F–(ii) What are the atomic numbers of elements whose outermost electrons are represented by (a) 3s1 (b) 2p3 and (c) 3p5?(iii) Which atoms are indicated by the following configurations?(a) [He] 2s1 (b) [Ne] 3s2 3p3 (c) [Ar] 4s2 3d1.

Last updated date: 19th Sep 2024
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Hint:

(i) The electronic configuration of an atom describes the distribution of its electrons in atomic orbitals. Ions are formed by gaining or losing electrons, which alters this configuration.

(ii) The atomic number is the number of protons in the nucleus of an atom, which determines the chemical properties of an element and its place in the periodic table.

(iii) Noble gas notation is a method to represent the electron configuration of an atom, which includes the noble gas symbol in square brackets and the additional electron configuration. This is a shorthand form to represent the electron configuration of an atom.

Step-by-step Solution:

(i) Electronic configurations of the given ions:

(a) H−: The hydrogen atom has 1 electron. H− gains one more electron, making it 2 electrons. Its configuration is similar to helium.

Configuration: $1s^2$

(b) Na+: Sodium atom has 11 electrons. Na+ means it has lost one electron.

Configuration for Na atom: $1s^2 2s^2 2p^6 3s^1\\$

Configuration for Na+: $1s^2 2s^2 2p^6\\$

(c) O2−: Oxygen atom has 8 electrons. O2− means it has gained two more electrons.

Configuration for O atom: $1s^2 2s^2 2p^4\\$

Configuration for O2−: $1s^2 2s^2 2p^6\\$

(d) F−: Fluorine atom has 9 electrons. F− means it has gained one more electron.

Configuration: $1s^2 2s^2 2p^6\\$

(ii) Atomic numbers for the given configurations:

(a) $3s^1$: The atomic number is 11, which belongs to Sodium (Na).

(b) $2p^3$: The atomic number is 7, which belongs to Nitrogen (N).

(c) $3p^5$: The atomic number is 17, which belongs to Chlorine (Cl).

(iii) Atoms represented by the given configurations:

(a) [He] 2s^1: This is the configuration for an element with 3 electrons, which is Lithium (Li).

(b) [Ne] 3s^2 3p^3: This is the configuration for an element with 15 electrons, which is Phosphorus (P).

(c) [Ar] 4s^2 3d^1: This is the configuration for an element with 21 electrons, which is Scandium (Sc).

Note: The configuration of an atom can give us insights into the element's properties, its position in the periodic table, and its behavior in chemical reactions. Noble gas notation (using symbols like [He], [Ne], etc.) is a shortcut used to write configurations of elements that come after the noble gases in the periodic table, highlighting the core electrons represented by the noble gas and the valence electrons that differentiate the atom from that noble gas.