{"id":86293,"date":"2025-06-01T03:42:48","date_gmt":"2025-06-01T03:42:48","guid":{"rendered":"https:\/\/exam.pscnotes.com\/mcq\/?p=86293"},"modified":"2025-06-01T03:42:48","modified_gmt":"2025-06-01T03:42:48","slug":"cl-is-not-isoelectronic-with","status":"publish","type":"post","link":"https:\/\/exam.pscnotes.com\/mcq\/cl-is-not-isoelectronic-with\/","title":{"rendered":"Cl$^{-}$ is not isoelectronic with"},"content":{"rendered":"

Cl$^{-}$ is not<\/b> isoelectronic with<\/p>\n

[amp_mcq option1=”K$^{+}$” option2=”Mg$^{2+}$” option3=”S$^{2-}$” option4=”P$^{3-}$” correct=”option2″]<\/p>\n

\n
\n
This question was previously asked in<\/div>\n
UPSC CDS-2 – 2022<\/div>\n<\/div>\n
Download PDF<\/a>Attempt Online<\/a><\/div>\n<\/div>\n
\nIsoelectronic species are atoms or ions that have the same number of electrons. Cl$^{-}$ has an atomic number of 17, so Cl has 17 electrons. Cl$^{-}$ has gained one electron, giving it 17 + 1 = 18 electrons. We need to find the species among the options that does not have 18 electrons.
\n<\/section>\n
\n– K$^{+}$: Atomic number of K is 19. K$^{+}$ has lost one electron, so it has 19 – 1 = 18 electrons.
\n– Mg$^{2+}$: Atomic number of Mg is 12. Mg$^{2+}$ has lost two electrons, so it has 12 – 2 = 10 electrons.
\n– S$^{2-}$: Atomic number of S is 16. S$^{2-}$ has gained two electrons, so it has 16 + 2 = 18 electrons.
\n– P$^{3-}$: Atomic number of P is 15. P$^{3-}$ has gained three electrons, so it has 15 + 3 = 18 electrons.
\nThus, Cl$^{-}$ (18 electrons) is not isoelectronic with Mg$^{2+}$ (10 electrons).
\n<\/section>\n
\nOther common isoelectronic series with 18 electrons include Ar, Ca$^{2+}$, Sc$^{3+}$. The electronic configuration for all species with 18 electrons is 1s\u00b22s\u00b22p\u20763s\u00b23p\u2076, which is the electron configuration of the noble gas Argon.
\n<\/section>\n","protected":false},"excerpt":{"rendered":"

Cl$^{-}$ is not isoelectronic with [amp_mcq option1=”K$^{+}$” option2=”Mg$^{2+}$” option3=”S$^{2-}$” option4=”P$^{3-}$” correct=”option2″] This question was previously asked in UPSC CDS-2 – 2022 Download PDFAttempt Online Isoelectronic species are atoms or ions that have the same number of electrons. Cl$^{-}$ has an atomic number of 17, so Cl has 17 electrons. Cl$^{-}$ has gained one electron, giving … <\/p>\n

Detailed SolutionCl$^{-}$ is not isoelectronic with<\/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":[1088],"tags":[1108,1162,1096],"class_list":["post-86293","post","type-post","status-publish","format-standard","hentry","category-upsc-cds-2","tag-1108","tag-atomic-structure","tag-chemistry","no-featured-image-padding"],"yoast_head":"\nCl$^{-}$ is not isoelectronic with<\/title>\n<meta name=\"description\" content=\"Isoelectronic species are atoms or ions that have the same number of electrons. Cl$^{-}$ has an atomic number of 17, so Cl has 17 electrons. Cl$^{-}$ has gained one electron, giving it 17 + 1 = 18 electrons. We need to find the species among the options that does not have 18 electrons. - K$^{+}$: Atomic number of K is 19. K$^{+}$ has lost one electron, so it has 19 - 1 = 18 electrons. - Mg$^{2+}$: Atomic number of Mg is 12. Mg$^{2+}$ has lost two electrons, so it has 12 - 2 = 10 electrons. - S$^{2-}$: Atomic number of S is 16. S$^{2-}$ has gained two electrons, so it has 16 + 2 = 18 electrons. - P$^{3-}$: Atomic number of P is 15. P$^{3-}$ has gained three electrons, so it has 15 + 3 = 18 electrons. Thus, Cl$^{-}$ (18 electrons) is not isoelectronic with Mg$^{2+}$ (10 electrons).\" \/>\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\/cl-is-not-isoelectronic-with\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Cl$^{-}$ is not isoelectronic with\" \/>\n<meta property=\"og:description\" content=\"Isoelectronic species are atoms or ions that have the same number of electrons. Cl$^{-}$ has an atomic number of 17, so Cl has 17 electrons. Cl$^{-}$ has gained one electron, giving it 17 + 1 = 18 electrons. We need to find the species among the options that does not have 18 electrons. - K$^{+}$: Atomic number of K is 19. K$^{+}$ has lost one electron, so it has 19 - 1 = 18 electrons. - Mg$^{2+}$: Atomic number of Mg is 12. Mg$^{2+}$ has lost two electrons, so it has 12 - 2 = 10 electrons. - S$^{2-}$: Atomic number of S is 16. S$^{2-}$ has gained two electrons, so it has 16 + 2 = 18 electrons. - P$^{3-}$: Atomic number of P is 15. P$^{3-}$ has gained three electrons, so it has 15 + 3 = 18 electrons. Thus, Cl$^{-}$ (18 electrons) is not isoelectronic with Mg$^{2+}$ (10 electrons).\" \/>\n<meta property=\"og:url\" content=\"https:\/\/exam.pscnotes.com\/mcq\/cl-is-not-isoelectronic-with\/\" \/>\n<meta property=\"og:site_name\" content=\"MCQ and Quiz for Exams\" \/>\n<meta property=\"article:published_time\" content=\"2025-06-01T03:42:48+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":"Cl$^{-}$ is not isoelectronic with","description":"Isoelectronic species are atoms or ions that have the same number of electrons. Cl$^{-}$ has an atomic number of 17, so Cl has 17 electrons. Cl$^{-}$ has gained one electron, giving it 17 + 1 = 18 electrons. We need to find the species among the options that does not have 18 electrons. - K$^{+}$: Atomic number of K is 19. K$^{+}$ has lost one electron, so it has 19 - 1 = 18 electrons. - Mg$^{2+}$: Atomic number of Mg is 12. Mg$^{2+}$ has lost two electrons, so it has 12 - 2 = 10 electrons. - S$^{2-}$: Atomic number of S is 16. S$^{2-}$ has gained two electrons, so it has 16 + 2 = 18 electrons. - P$^{3-}$: Atomic number of P is 15. P$^{3-}$ has gained three electrons, so it has 15 + 3 = 18 electrons. Thus, Cl$^{-}$ (18 electrons) is not isoelectronic with Mg$^{2+}$ (10 electrons).","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\/cl-is-not-isoelectronic-with\/","og_locale":"en_US","og_type":"article","og_title":"Cl$^{-}$ is not isoelectronic with","og_description":"Isoelectronic species are atoms or ions that have the same number of electrons. Cl$^{-}$ has an atomic number of 17, so Cl has 17 electrons. Cl$^{-}$ has gained one electron, giving it 17 + 1 = 18 electrons. We need to find the species among the options that does not have 18 electrons. - K$^{+}$: Atomic number of K is 19. K$^{+}$ has lost one electron, so it has 19 - 1 = 18 electrons. - Mg$^{2+}$: Atomic number of Mg is 12. Mg$^{2+}$ has lost two electrons, so it has 12 - 2 = 10 electrons. - S$^{2-}$: Atomic number of S is 16. S$^{2-}$ has gained two electrons, so it has 16 + 2 = 18 electrons. - P$^{3-}$: Atomic number of P is 15. P$^{3-}$ has gained three electrons, so it has 15 + 3 = 18 electrons. Thus, Cl$^{-}$ (18 electrons) is not isoelectronic with Mg$^{2+}$ (10 electrons).","og_url":"https:\/\/exam.pscnotes.com\/mcq\/cl-is-not-isoelectronic-with\/","og_site_name":"MCQ and Quiz for Exams","article_published_time":"2025-06-01T03:42:48+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\/cl-is-not-isoelectronic-with\/","url":"https:\/\/exam.pscnotes.com\/mcq\/cl-is-not-isoelectronic-with\/","name":"Cl$^{-}$ is not isoelectronic with","isPartOf":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#website"},"datePublished":"2025-06-01T03:42:48+00:00","dateModified":"2025-06-01T03:42:48+00:00","author":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/5807dafeb27d2ec82344d6cbd6c3d209"},"description":"Isoelectronic species are atoms or ions that have the same number of electrons. Cl$^{-}$ has an atomic number of 17, so Cl has 17 electrons. Cl$^{-}$ has gained one electron, giving it 17 + 1 = 18 electrons. We need to find the species among the options that does not have 18 electrons. - K$^{+}$: Atomic number of K is 19. K$^{+}$ has lost one electron, so it has 19 - 1 = 18 electrons. - Mg$^{2+}$: Atomic number of Mg is 12. Mg$^{2+}$ has lost two electrons, so it has 12 - 2 = 10 electrons. - S$^{2-}$: Atomic number of S is 16. S$^{2-}$ has gained two electrons, so it has 16 + 2 = 18 electrons. - P$^{3-}$: Atomic number of P is 15. P$^{3-}$ has gained three electrons, so it has 15 + 3 = 18 electrons. Thus, Cl$^{-}$ (18 electrons) is not isoelectronic with Mg$^{2+}$ (10 electrons).","breadcrumb":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/cl-is-not-isoelectronic-with\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/exam.pscnotes.com\/mcq\/cl-is-not-isoelectronic-with\/"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/exam.pscnotes.com\/mcq\/cl-is-not-isoelectronic-with\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/exam.pscnotes.com\/mcq\/"},{"@type":"ListItem","position":2,"name":"UPSC CDS-2","item":"https:\/\/exam.pscnotes.com\/mcq\/category\/upsc-cds-2\/"},{"@type":"ListItem","position":3,"name":"Cl$^{-}$ is not isoelectronic with"}]},{"@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\/86293","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=86293"}],"version-history":[{"count":0,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts\/86293\/revisions"}],"wp:attachment":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/media?parent=86293"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/categories?post=86293"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/tags?post=86293"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}