{"id":84765,"date":"2025-06-01T02:49:30","date_gmt":"2025-06-01T02:49:30","guid":{"rendered":"https:\/\/exam.pscnotes.com\/mcq\/?p=84765"},"modified":"2025-06-01T02:49:30","modified_gmt":"2025-06-01T02:49:30","slug":"which-one-of-the-following-elements-will-be-an-isobar-of-calcium-if-th","status":"publish","type":"post","link":"https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-elements-will-be-an-isobar-of-calcium-if-th\/","title":{"rendered":"Which one of the following elements will be an isobar of calcium if th"},"content":{"rendered":"<p>Which one of the following elements will be an isobar of calcium if the atomic number of calcium is 20 and its mass number is 40?<\/p>\n<p>[amp_mcq option1=&#8221;Element with 20 protons and 18 neutrons&#8221; option2=&#8221;Element with 18 protons and 19 neutrons&#8221; option3=&#8221;Element with 20 protons and 19 neutrons&#8221; option4=&#8221;Element with 18 protons and 22 neutrons&#8221; correct=&#8221;option4&#8243;]<\/p>\n<div class=\"psc-box-pyq-exam-year-detail\">\n<div class=\"pyq-exam\">\n<div class=\"psc-heading\">This question was previously asked in<\/div>\n<div class=\"psc-title line-ellipsis\">UPSC CDS-1 &#8211; 2018<\/div>\n<\/div>\n<div class=\"pyq-exam-psc-buttons\"><a href=\"\/pyq\/pyq-upsc-cds-1-2018.pdf\" target=\"_blank\" class=\"psc-pdf-button\" rel=\"noopener\">Download PDF<\/a><a href=\"\/pyq-upsc-cds-1-2018\" target=\"_blank\" class=\"psc-attempt-button\" rel=\"noopener\">Attempt Online<\/a><\/div>\n<\/div>\n<section id=\"pyq-correct-answer\">\nIsobars are atoms of different elements that have the same mass number (total number of protons and neutrons) but different atomic numbers (number of protons).<br \/>\nCalcium (Ca) has atomic number (Z) = 20 and mass number (A) = 40.<br \/>\nAn isobar of Calcium-40 must have a mass number of 40 but an atomic number different from 20.<br \/>\nLet&#8217;s examine the options:<br \/>\nA) 20 protons, 18 neutrons: Z=20, A=20+18=38. (Isotope of Ca)<br \/>\nB) 18 protons, 19 neutrons: Z=18 (Argon), A=18+19=37. (Argon-37)<br \/>\nC) 20 protons, 19 neutrons: Z=20, A=20+19=39. (Isotope of Ca)<br \/>\nD) 18 protons, 22 neutrons: Z=18 (Argon), A=18+22=40. (Argon-40). This element has a different atomic number (18) but the same mass number (40) as Calcium-40. Thus, Argon-40 is an isobar of Calcium-40.<br \/>\n<\/section>\n<section id=\"pyq-key-points\">\nIsobars have the same mass number but different atomic numbers.<br \/>\n<\/section>\n<section id=\"pyq-additional-information\">\nIsotopes have the same atomic number but different mass numbers. Isotones have the same number of neutrons but different atomic numbers and mass numbers.<br \/>\n<\/section>\n","protected":false},"excerpt":{"rendered":"<p>Which one of the following elements will be an isobar of calcium if the atomic number of calcium is 20 and its mass number is 40? [amp_mcq option1=&#8221;Element with 20 protons and 18 neutrons&#8221; option2=&#8221;Element with 18 protons and 19 neutrons&#8221; option3=&#8221;Element with 20 protons and 19 neutrons&#8221; option4=&#8221;Element with 18 protons and 22 neutrons&#8221; &#8230; <\/p>\n<p class=\"read-more-container\"><a title=\"Which one of the following elements will be an isobar of calcium if th\" class=\"read-more button\" href=\"https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-elements-will-be-an-isobar-of-calcium-if-th\/#more-84765\">Detailed Solution<span class=\"screen-reader-text\">Which one of the following elements will be an isobar of calcium if th<\/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":[1087],"tags":[1114,1162,1096],"class_list":["post-84765","post","type-post","status-publish","format-standard","hentry","category-upsc-cds-1","tag-1114","tag-atomic-structure","tag-chemistry","no-featured-image-padding"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v22.2 (Yoast SEO v23.3) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Which one of the following elements will be an isobar of calcium if th<\/title>\n<meta name=\"description\" content=\"Isobars are atoms of different elements that have the same mass number (total number of protons and neutrons) but different atomic numbers (number of protons). Calcium (Ca) has atomic number (Z) = 20 and mass number (A) = 40. An isobar of Calcium-40 must have a mass number of 40 but an atomic number different from 20. Let&#039;s examine the options: A) 20 protons, 18 neutrons: Z=20, A=20+18=38. (Isotope of Ca) B) 18 protons, 19 neutrons: Z=18 (Argon), A=18+19=37. (Argon-37) C) 20 protons, 19 neutrons: Z=20, A=20+19=39. (Isotope of Ca) D) 18 protons, 22 neutrons: Z=18 (Argon), A=18+22=40. (Argon-40). This element has a different atomic number (18) but the same mass number (40) as Calcium-40. Thus, Argon-40 is an isobar of Calcium-40. Isobars have the same mass number but different atomic numbers.\" \/>\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\/which-one-of-the-following-elements-will-be-an-isobar-of-calcium-if-th\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Which one of the following elements will be an isobar of calcium if th\" \/>\n<meta property=\"og:description\" content=\"Isobars are atoms of different elements that have the same mass number (total number of protons and neutrons) but different atomic numbers (number of protons). Calcium (Ca) has atomic number (Z) = 20 and mass number (A) = 40. An isobar of Calcium-40 must have a mass number of 40 but an atomic number different from 20. Let&#039;s examine the options: A) 20 protons, 18 neutrons: Z=20, A=20+18=38. (Isotope of Ca) B) 18 protons, 19 neutrons: Z=18 (Argon), A=18+19=37. (Argon-37) C) 20 protons, 19 neutrons: Z=20, A=20+19=39. (Isotope of Ca) D) 18 protons, 22 neutrons: Z=18 (Argon), A=18+22=40. (Argon-40). This element has a different atomic number (18) but the same mass number (40) as Calcium-40. Thus, Argon-40 is an isobar of Calcium-40. Isobars have the same mass number but different atomic numbers.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-elements-will-be-an-isobar-of-calcium-if-th\/\" \/>\n<meta property=\"og:site_name\" content=\"MCQ and Quiz for Exams\" \/>\n<meta property=\"article:published_time\" content=\"2025-06-01T02:49:30+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":"Which one of the following elements will be an isobar of calcium if th","description":"Isobars are atoms of different elements that have the same mass number (total number of protons and neutrons) but different atomic numbers (number of protons). Calcium (Ca) has atomic number (Z) = 20 and mass number (A) = 40. An isobar of Calcium-40 must have a mass number of 40 but an atomic number different from 20. Let's examine the options: A) 20 protons, 18 neutrons: Z=20, A=20+18=38. (Isotope of Ca) B) 18 protons, 19 neutrons: Z=18 (Argon), A=18+19=37. (Argon-37) C) 20 protons, 19 neutrons: Z=20, A=20+19=39. (Isotope of Ca) D) 18 protons, 22 neutrons: Z=18 (Argon), A=18+22=40. (Argon-40). This element has a different atomic number (18) but the same mass number (40) as Calcium-40. Thus, Argon-40 is an isobar of Calcium-40. Isobars have the same mass number but different atomic numbers.","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\/which-one-of-the-following-elements-will-be-an-isobar-of-calcium-if-th\/","og_locale":"en_US","og_type":"article","og_title":"Which one of the following elements will be an isobar of calcium if th","og_description":"Isobars are atoms of different elements that have the same mass number (total number of protons and neutrons) but different atomic numbers (number of protons). Calcium (Ca) has atomic number (Z) = 20 and mass number (A) = 40. An isobar of Calcium-40 must have a mass number of 40 but an atomic number different from 20. Let's examine the options: A) 20 protons, 18 neutrons: Z=20, A=20+18=38. (Isotope of Ca) B) 18 protons, 19 neutrons: Z=18 (Argon), A=18+19=37. (Argon-37) C) 20 protons, 19 neutrons: Z=20, A=20+19=39. (Isotope of Ca) D) 18 protons, 22 neutrons: Z=18 (Argon), A=18+22=40. (Argon-40). This element has a different atomic number (18) but the same mass number (40) as Calcium-40. Thus, Argon-40 is an isobar of Calcium-40. Isobars have the same mass number but different atomic numbers.","og_url":"https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-elements-will-be-an-isobar-of-calcium-if-th\/","og_site_name":"MCQ and Quiz for Exams","article_published_time":"2025-06-01T02:49:30+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\/which-one-of-the-following-elements-will-be-an-isobar-of-calcium-if-th\/","url":"https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-elements-will-be-an-isobar-of-calcium-if-th\/","name":"Which one of the following elements will be an isobar of calcium if th","isPartOf":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#website"},"datePublished":"2025-06-01T02:49:30+00:00","dateModified":"2025-06-01T02:49:30+00:00","author":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/5807dafeb27d2ec82344d6cbd6c3d209"},"description":"Isobars are atoms of different elements that have the same mass number (total number of protons and neutrons) but different atomic numbers (number of protons). Calcium (Ca) has atomic number (Z) = 20 and mass number (A) = 40. An isobar of Calcium-40 must have a mass number of 40 but an atomic number different from 20. Let's examine the options: A) 20 protons, 18 neutrons: Z=20, A=20+18=38. (Isotope of Ca) B) 18 protons, 19 neutrons: Z=18 (Argon), A=18+19=37. (Argon-37) C) 20 protons, 19 neutrons: Z=20, A=20+19=39. (Isotope of Ca) D) 18 protons, 22 neutrons: Z=18 (Argon), A=18+22=40. (Argon-40). This element has a different atomic number (18) but the same mass number (40) as Calcium-40. Thus, Argon-40 is an isobar of Calcium-40. Isobars have the same mass number but different atomic numbers.","breadcrumb":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-elements-will-be-an-isobar-of-calcium-if-th\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-elements-will-be-an-isobar-of-calcium-if-th\/"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-elements-will-be-an-isobar-of-calcium-if-th\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/exam.pscnotes.com\/mcq\/"},{"@type":"ListItem","position":2,"name":"UPSC CDS-1","item":"https:\/\/exam.pscnotes.com\/mcq\/category\/upsc-cds-1\/"},{"@type":"ListItem","position":3,"name":"Which one of the following elements will be an isobar of calcium if th"}]},{"@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\/84765","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=84765"}],"version-history":[{"count":0,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts\/84765\/revisions"}],"wp:attachment":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/media?parent=84765"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/categories?post=84765"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/tags?post=84765"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}