{"id":185875,"date":"2025-01-23T11:33:07","date_gmt":"2025-01-23T11:33:07","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=185875"},"modified":"2025-01-23T11:33:09","modified_gmt":"2025-01-23T11:33:09","slug":"which-ion-of-na-k-mg2-ca2-rb-has-the-smallest-radius","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/01\/23\/which-ion-of-na-k-mg2-ca2-rb-has-the-smallest-radius\/","title":{"rendered":"Which ion of Na+, K+, Mg2+, Ca2+, Rb+ has the smallest radius"},"content":{"rendered":"\n

Which ion of Na+, K+, Mg2+, Ca2+, Rb+ has the smallest radius? Which one
has the largest? Explain the reasons.<\/p>\n\n\n\n

The Correct Answer and Explanation is :<\/strong><\/mark><\/p>\n\n\n\n

The ion with the smallest radius among Na+, K+, Mg\u00b2\u207a, Ca\u00b2\u207a, and Rb+ is Mg\u00b2\u207a<\/strong>, and the ion with the largest radius is Rb+<\/strong>.<\/p>\n\n\n\n

Reasoning:<\/h3>\n\n\n\n
    \n
  1. Ionic Size and Effective Nuclear Charge (Z_eff):<\/strong>
    Ionic radii are influenced by two main factors: the effective nuclear charge (Z_eff)<\/strong> and the electron-electron repulsion<\/strong>. Z_eff refers to the net positive charge that an electron experiences from the nucleus, taking into account the shielding effects of other electrons.<\/li>\n\n\n\n
  2. Cations and Their Sizes:<\/strong>
    All the ions listed (Na+, K+, Mg\u00b2\u207a, Ca\u00b2\u207a, and Rb+) are positively charged (cations), meaning they have lost one or more electrons. The loss of electrons results in a decrease in electron-electron repulsion, causing the ion to contract, but the extent of contraction depends on the effective nuclear charge and the number of electrons remaining.<\/li>\n\n\n\n
  3. Mg\u00b2\u207a (Smallest Radius):<\/strong><\/li>\n<\/ol>\n\n\n\n
      \n
    • Magnesium (Mg)<\/strong> has an atomic number of 12 and typically has the electron configuration [Ne] 3s\u00b2. When it loses two electrons to become Mg\u00b2\u207a, it attains the electron configuration of neon ([Ne]), with only 10 electrons but still a nucleus with 12 protons.<\/li>\n\n\n\n
    • The higher charge on the nucleus (12 protons) exerts a strong attractive force on the remaining 10 electrons, pulling them closer. Therefore, Mg\u00b2\u207a is very compact, with a small ionic radius.<\/li>\n<\/ul>\n\n\n\n
        \n
      1. Rb+ (Largest Radius):<\/strong><\/li>\n<\/ol>\n\n\n\n
          \n
        • Rubidium (Rb)<\/strong> has an atomic number of 37, and its electron configuration is [Kr] 5s\u00b9. Upon losing one electron to form Rb+, it attains the configuration [Kr], but it still has 37 protons attracting only 36 electrons.<\/li>\n\n\n\n
        • The electron cloud of Rb+ is much larger because the remaining electrons are further from the nucleus due to Rb\u2019s lower Z_eff and the larger size of the atom. Thus, Rb+ has the largest ionic radius.<\/li>\n<\/ul>\n\n\n\n

          Trend of Ionic Radii:<\/h3>\n\n\n\n

          The trend of ionic radius is influenced by:<\/p>\n\n\n\n

            \n
          • Charge<\/strong>: Higher charges result in a smaller ionic radius (because the nucleus pulls electrons more tightly).<\/li>\n\n\n\n
          • Electron Configuration<\/strong>: Ions with more protons relative to the number of electrons tend to have smaller radii because of stronger attraction.<\/li>\n<\/ul>\n\n\n\n

            Thus, among the ions, Mg\u00b2\u207a<\/strong> has the smallest radius due to its high charge and small electron cloud, and Rb+<\/strong> has the largest radius because of its lower effective nuclear charge and larger atomic size.<\/p>\n","protected":false},"excerpt":{"rendered":"

            Which ion of Na+, K+, Mg2+, Ca2+, Rb+ has the smallest radius? Which onehas the largest? Explain the reasons. The Correct Answer and Explanation is : The ion with the smallest radius among Na+, K+, Mg\u00b2\u207a, Ca\u00b2\u207a, and Rb+ is Mg\u00b2\u207a, and the ion with the largest radius is Rb+. Reasoning: Trend of Ionic Radii: […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-185875","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/185875","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=185875"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/185875\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=185875"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=185875"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=185875"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}