{"id":87645,"date":"2025-06-01T06:50:19","date_gmt":"2025-06-01T06:50:19","guid":{"rendered":"https:\/\/exam.pscnotes.com\/mcq\/?p=87645"},"modified":"2025-06-01T06:50:19","modified_gmt":"2025-06-01T06:50:19","slug":"in-which-of-the-following-pairs-are-the-ions-isoelectronic","status":"publish","type":"post","link":"https:\/\/exam.pscnotes.com\/mcq\/in-which-of-the-following-pairs-are-the-ions-isoelectronic\/","title":{"rendered":"In which of the following pairs are the ions isoelectronic ?"},"content":{"rendered":"

In which of the following pairs are the ions isoelectronic ?<\/p>\n

[amp_mcq option1=”Mg$^{2+}$, Ar” option2=”Na$^{+}$, O$^{2-}$” option3=”Al$^{3+}$, Cl$^{-}$” option4=”K$^{+}$, Ne” correct=”option2″]<\/p>\n

\n
\n
This question was previously asked in<\/div>\n
UPSC NDA-1 – 2019<\/div>\n<\/div>\n
Download PDF<\/a>Attempt Online<\/a><\/div>\n<\/div>\n
\nThe pair Na\u207a and O\u00b2\u207b are isoelectronic.
\n<\/section>\n
\nIsoelectronic species are atoms or ions that have the same number of electrons. Let’s check the electron count for each species:
\n– Mg\u00b2\u207a: Magnesium (Mg) has atomic number 12, so it has 12 electrons. Mg\u00b2\u207a has lost 2 electrons, so it has 10 electrons.
\n– Ar: Argon (Ar) has atomic number 18, so it has 18 electrons.
\n– Na\u207a: Sodium (Na) has atomic number 11, so it has 11 electrons. Na\u207a has lost 1 electron, so it has 10 electrons.
\n– O\u00b2\u207b: Oxygen (O) has atomic number 8, so it has 8 electrons. O\u00b2\u207b has gained 2 electrons, so it has 10 electrons.
\n– Al\u00b3\u207a: Aluminum (Al) has atomic number 13, so it has 13 electrons. Al\u00b3\u207a has lost 3 electrons, so it has 10 electrons.
\n– Cl\u207b: Chlorine (Cl) has atomic number 17, so it has 17 electrons. Cl\u207b has gained 1 electron, so it has 18 electrons.
\n– K\u207a: Potassium (K) has atomic number 19, so it has 19 electrons. K\u207a has lost 1 electron, so it has 18 electrons.
\n– Ne: Neon (Ne) has atomic number 10, so it has 10 electrons.<\/p>\n

Comparing the pairs:
\nA) Mg\u00b2\u207a (10e\u207b), Ar (18e\u207b) – Not isoelectronic.
\nB) Na\u207a (10e\u207b), O\u00b2\u207b (10e\u207b) – Isoelectronic.
\nC) Al\u00b3\u207a (10e\u207b), Cl\u207b (18e\u207b) – Not isoelectronic.
\nD) K\u207a (18e\u207b), Ne (10e\u207b) – Not isoelectronic.
\n<\/section>\n

\nMany ions of elements close to noble gases are isoelectronic with the nearest noble gas. For example, Na\u207a, Mg\u00b2\u207a, Al\u00b3\u207a, O\u00b2\u207b, F\u207b are all isoelectronic with Neon (10 electrons). K\u207a, Ca\u00b2\u207a, S\u00b2\u207b, Cl\u207b are all isoelectronic with Argon (18 electrons). Isoelectronic species often have similar chemical properties related to their electron configuration.
\n<\/section>\n","protected":false},"excerpt":{"rendered":"

In which of the following pairs are the ions isoelectronic ? [amp_mcq option1=”Mg$^{2+}$, Ar” option2=”Na$^{+}$, O$^{2-}$” option3=”Al$^{3+}$, Cl$^{-}$” option4=”K$^{+}$, Ne” correct=”option2″] This question was previously asked in UPSC NDA-1 – 2019 Download PDFAttempt Online The pair Na\u207a and O\u00b2\u207b are isoelectronic. Isoelectronic species are atoms or ions that have the same number of electrons. Let’s … <\/p>\n

Detailed SolutionIn which of the following pairs are the ions isoelectronic ?<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1093],"tags":[1119,1162,1096],"class_list":["post-87645","post","type-post","status-publish","format-standard","hentry","category-upsc-nda-1","tag-1119","tag-atomic-structure","tag-chemistry","no-featured-image-padding"],"yoast_head":"\nIn which of the following pairs are the ions isoelectronic ?<\/title>\n<meta name=\"description\" content=\"The pair Na\u207a and O\u00b2\u207b are isoelectronic. Isoelectronic species are atoms or ions that have the same number of electrons. Let's check the electron count for each species: - Mg\u00b2\u207a: Magnesium (Mg) has atomic number 12, so it has 12 electrons. Mg\u00b2\u207a has lost 2 electrons, so it has 10 electrons. - Ar: Argon (Ar) has atomic number 18, so it has 18 electrons. - Na\u207a: Sodium (Na) has atomic number 11, so it has 11 electrons. Na\u207a has lost 1 electron, so it has 10 electrons. - O\u00b2\u207b: Oxygen (O) has atomic number 8, so it has 8 electrons. O\u00b2\u207b has gained 2 electrons, so it has 10 electrons. - Al\u00b3\u207a: Aluminum (Al) has atomic number 13, so it has 13 electrons. Al\u00b3\u207a has lost 3 electrons, so it has 10 electrons. - Cl\u207b: Chlorine (Cl) has atomic number 17, so it has 17 electrons. Cl\u207b has gained 1 electron, so it has 18 electrons. - K\u207a: Potassium (K) has atomic number 19, so it has 19 electrons. K\u207a has lost 1 electron, so it has 18 electrons. - Ne: Neon (Ne) has atomic number 10, so it has 10 electrons. Comparing the pairs: A) Mg\u00b2\u207a (10e\u207b), Ar (18e\u207b) - Not isoelectronic. B) Na\u207a (10e\u207b), O\u00b2\u207b (10e\u207b) - Isoelectronic. C) Al\u00b3\u207a (10e\u207b), Cl\u207b (18e\u207b) - Not isoelectronic. D) K\u207a (18e\u207b), Ne (10e\u207b) - Not isoelectronic.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/exam.pscnotes.com\/mcq\/in-which-of-the-following-pairs-are-the-ions-isoelectronic\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"In which of the following pairs are the ions isoelectronic ?\" \/>\n<meta property=\"og:description\" content=\"The pair Na\u207a and O\u00b2\u207b are isoelectronic. Isoelectronic species are atoms or ions that have the same number of electrons. Let's check the electron count for each species: - Mg\u00b2\u207a: Magnesium (Mg) has atomic number 12, so it has 12 electrons. Mg\u00b2\u207a has lost 2 electrons, so it has 10 electrons. - Ar: Argon (Ar) has atomic number 18, so it has 18 electrons. - Na\u207a: Sodium (Na) has atomic number 11, so it has 11 electrons. Na\u207a has lost 1 electron, so it has 10 electrons. - O\u00b2\u207b: Oxygen (O) has atomic number 8, so it has 8 electrons. O\u00b2\u207b has gained 2 electrons, so it has 10 electrons. - Al\u00b3\u207a: Aluminum (Al) has atomic number 13, so it has 13 electrons. Al\u00b3\u207a has lost 3 electrons, so it has 10 electrons. - Cl\u207b: Chlorine (Cl) has atomic number 17, so it has 17 electrons. Cl\u207b has gained 1 electron, so it has 18 electrons. - K\u207a: Potassium (K) has atomic number 19, so it has 19 electrons. K\u207a has lost 1 electron, so it has 18 electrons. - Ne: Neon (Ne) has atomic number 10, so it has 10 electrons. Comparing the pairs: A) Mg\u00b2\u207a (10e\u207b), Ar (18e\u207b) - Not isoelectronic. B) Na\u207a (10e\u207b), O\u00b2\u207b (10e\u207b) - Isoelectronic. C) Al\u00b3\u207a (10e\u207b), Cl\u207b (18e\u207b) - Not isoelectronic. D) K\u207a (18e\u207b), Ne (10e\u207b) - Not isoelectronic.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/exam.pscnotes.com\/mcq\/in-which-of-the-following-pairs-are-the-ions-isoelectronic\/\" \/>\n<meta property=\"og:site_name\" content=\"MCQ and Quiz for Exams\" \/>\n<meta property=\"article:published_time\" content=\"2025-06-01T06:50:19+00:00\" \/>\n<meta name=\"author\" content=\"rawan239\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"rawan239\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"In which of the following pairs are the ions isoelectronic ?","description":"The pair Na\u207a and O\u00b2\u207b are isoelectronic. Isoelectronic species are atoms or ions that have the same number of electrons. Let's check the electron count for each species: - Mg\u00b2\u207a: Magnesium (Mg) has atomic number 12, so it has 12 electrons. Mg\u00b2\u207a has lost 2 electrons, so it has 10 electrons. - Ar: Argon (Ar) has atomic number 18, so it has 18 electrons. - Na\u207a: Sodium (Na) has atomic number 11, so it has 11 electrons. Na\u207a has lost 1 electron, so it has 10 electrons. - O\u00b2\u207b: Oxygen (O) has atomic number 8, so it has 8 electrons. O\u00b2\u207b has gained 2 electrons, so it has 10 electrons. - Al\u00b3\u207a: Aluminum (Al) has atomic number 13, so it has 13 electrons. Al\u00b3\u207a has lost 3 electrons, so it has 10 electrons. - Cl\u207b: Chlorine (Cl) has atomic number 17, so it has 17 electrons. Cl\u207b has gained 1 electron, so it has 18 electrons. - K\u207a: Potassium (K) has atomic number 19, so it has 19 electrons. K\u207a has lost 1 electron, so it has 18 electrons. - Ne: Neon (Ne) has atomic number 10, so it has 10 electrons. Comparing the pairs: A) Mg\u00b2\u207a (10e\u207b), Ar (18e\u207b) - Not isoelectronic. B) Na\u207a (10e\u207b), O\u00b2\u207b (10e\u207b) - Isoelectronic. C) Al\u00b3\u207a (10e\u207b), Cl\u207b (18e\u207b) - Not isoelectronic. D) K\u207a (18e\u207b), Ne (10e\u207b) - Not isoelectronic.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/exam.pscnotes.com\/mcq\/in-which-of-the-following-pairs-are-the-ions-isoelectronic\/","og_locale":"en_US","og_type":"article","og_title":"In which of the following pairs are the ions isoelectronic ?","og_description":"The pair Na\u207a and O\u00b2\u207b are isoelectronic. Isoelectronic species are atoms or ions that have the same number of electrons. Let's check the electron count for each species: - Mg\u00b2\u207a: Magnesium (Mg) has atomic number 12, so it has 12 electrons. Mg\u00b2\u207a has lost 2 electrons, so it has 10 electrons. - Ar: Argon (Ar) has atomic number 18, so it has 18 electrons. - Na\u207a: Sodium (Na) has atomic number 11, so it has 11 electrons. Na\u207a has lost 1 electron, so it has 10 electrons. - O\u00b2\u207b: Oxygen (O) has atomic number 8, so it has 8 electrons. O\u00b2\u207b has gained 2 electrons, so it has 10 electrons. - Al\u00b3\u207a: Aluminum (Al) has atomic number 13, so it has 13 electrons. Al\u00b3\u207a has lost 3 electrons, so it has 10 electrons. - Cl\u207b: Chlorine (Cl) has atomic number 17, so it has 17 electrons. Cl\u207b has gained 1 electron, so it has 18 electrons. - K\u207a: Potassium (K) has atomic number 19, so it has 19 electrons. K\u207a has lost 1 electron, so it has 18 electrons. - Ne: Neon (Ne) has atomic number 10, so it has 10 electrons. Comparing the pairs: A) Mg\u00b2\u207a (10e\u207b), Ar (18e\u207b) - Not isoelectronic. B) Na\u207a (10e\u207b), O\u00b2\u207b (10e\u207b) - Isoelectronic. C) Al\u00b3\u207a (10e\u207b), Cl\u207b (18e\u207b) - Not isoelectronic. D) K\u207a (18e\u207b), Ne (10e\u207b) - Not isoelectronic.","og_url":"https:\/\/exam.pscnotes.com\/mcq\/in-which-of-the-following-pairs-are-the-ions-isoelectronic\/","og_site_name":"MCQ and Quiz for Exams","article_published_time":"2025-06-01T06:50:19+00:00","author":"rawan239","twitter_card":"summary_large_image","twitter_misc":{"Written by":"rawan239","Est. reading time":"1 minute"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/exam.pscnotes.com\/mcq\/in-which-of-the-following-pairs-are-the-ions-isoelectronic\/","url":"https:\/\/exam.pscnotes.com\/mcq\/in-which-of-the-following-pairs-are-the-ions-isoelectronic\/","name":"In which of the following pairs are the ions isoelectronic ?","isPartOf":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#website"},"datePublished":"2025-06-01T06:50:19+00:00","dateModified":"2025-06-01T06:50:19+00:00","author":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/5807dafeb27d2ec82344d6cbd6c3d209"},"description":"The pair Na\u207a and O\u00b2\u207b are isoelectronic. Isoelectronic species are atoms or ions that have the same number of electrons. Let's check the electron count for each species: - Mg\u00b2\u207a: Magnesium (Mg) has atomic number 12, so it has 12 electrons. Mg\u00b2\u207a has lost 2 electrons, so it has 10 electrons. - Ar: Argon (Ar) has atomic number 18, so it has 18 electrons. - Na\u207a: Sodium (Na) has atomic number 11, so it has 11 electrons. Na\u207a has lost 1 electron, so it has 10 electrons. - O\u00b2\u207b: Oxygen (O) has atomic number 8, so it has 8 electrons. O\u00b2\u207b has gained 2 electrons, so it has 10 electrons. - Al\u00b3\u207a: Aluminum (Al) has atomic number 13, so it has 13 electrons. Al\u00b3\u207a has lost 3 electrons, so it has 10 electrons. - Cl\u207b: Chlorine (Cl) has atomic number 17, so it has 17 electrons. Cl\u207b has gained 1 electron, so it has 18 electrons. - K\u207a: Potassium (K) has atomic number 19, so it has 19 electrons. K\u207a has lost 1 electron, so it has 18 electrons. - Ne: Neon (Ne) has atomic number 10, so it has 10 electrons. Comparing the pairs: A) Mg\u00b2\u207a (10e\u207b), Ar (18e\u207b) - Not isoelectronic. B) Na\u207a (10e\u207b), O\u00b2\u207b (10e\u207b) - Isoelectronic. C) Al\u00b3\u207a (10e\u207b), Cl\u207b (18e\u207b) - Not isoelectronic. D) K\u207a (18e\u207b), Ne (10e\u207b) - Not isoelectronic.","breadcrumb":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/in-which-of-the-following-pairs-are-the-ions-isoelectronic\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/exam.pscnotes.com\/mcq\/in-which-of-the-following-pairs-are-the-ions-isoelectronic\/"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/exam.pscnotes.com\/mcq\/in-which-of-the-following-pairs-are-the-ions-isoelectronic\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/exam.pscnotes.com\/mcq\/"},{"@type":"ListItem","position":2,"name":"UPSC NDA-1","item":"https:\/\/exam.pscnotes.com\/mcq\/category\/upsc-nda-1\/"},{"@type":"ListItem","position":3,"name":"In which of the following pairs are the ions isoelectronic ?"}]},{"@type":"WebSite","@id":"https:\/\/exam.pscnotes.com\/mcq\/#website","url":"https:\/\/exam.pscnotes.com\/mcq\/","name":"MCQ and Quiz for Exams","description":"","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/exam.pscnotes.com\/mcq\/?s={search_term_string}"},"query-input":"required name=search_term_string"}],"inLanguage":"en-US"},{"@type":"Person","@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/5807dafeb27d2ec82344d6cbd6c3d209","name":"rawan239","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/image\/","url":"https:\/\/secure.gravatar.com\/avatar\/761a7274f9cce048fa5b921221e7934820d74514df93ef195a9d22af0c1c9001?s=96&d=mm&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/761a7274f9cce048fa5b921221e7934820d74514df93ef195a9d22af0c1c9001?s=96&d=mm&r=g","caption":"rawan239"},"sameAs":["https:\/\/exam.pscnotes.com"],"url":"https:\/\/exam.pscnotes.com\/mcq\/author\/rawan239\/"}]}},"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts\/87645","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/comments?post=87645"}],"version-history":[{"count":0,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts\/87645\/revisions"}],"wp:attachment":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/media?parent=87645"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/categories?post=87645"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/tags?post=87645"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}