{"id":223866,"date":"2025-06-02T12:33:00","date_gmt":"2025-06-02T12:33:00","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=223866"},"modified":"2025-06-02T12:33:02","modified_gmt":"2025-06-02T12:33:02","slug":"why-and-how-are-elements-arranged-in-the-4th-period","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/06\/02\/why-and-how-are-elements-arranged-in-the-4th-period\/","title":{"rendered":"Why and how are elements arranged in the 4th period"},"content":{"rendered":"\n
Why and how are elements arranged in the 4th period? Why does the size of an atom not decrease regularly in a period? Give the trend of ionization energy in a period.<\/pre>\n\n\n\n
The Correct Answer and Explanation is:<\/mark><\/strong><\/p>\n\n\n\n
Why and How Are Elements Arranged in the 4th Period?<\/h3>\n\n\n\n
Elements in the 4th period<\/strong> of the periodic table are arranged in order of increasing atomic number<\/strong>, which means each subsequent element has one more proton and one more electron than the previous one. These electrons fill atomic orbitals according to the Aufbau principle<\/strong>, starting with the 4s orbital<\/strong>, then 3d<\/strong>, and finally 4p orbitals<\/strong>. This gives rise to the sequence:<\/p>\n\n\n\n
    \n
  • K (19) to Ca (20)<\/strong>: filling the 4s orbital<\/li>\n\n\n\n
  • Sc (21) to Zn (30)<\/strong>: filling the 3d orbitals (transition metals)<\/li>\n\n\n\n
  • Ga (31) to Kr (36)<\/strong>: filling the 4p orbitals<\/li>\n<\/ul>\n\n\n\n
    This arrangement ensures that chemical properties vary periodically and elements with similar outer electron configurations (and thus similar properties) fall into vertical groups.<\/p>\n\n\n\n
    \n\n\n\n
    Why Atomic Size Does Not Decrease Regularly Across a Period<\/h3>\n\n\n\n
    Generally, atomic size (or radius) decreases across a period<\/strong> due to the increasing nuclear charge (more protons), which pulls electrons closer to the nucleus. However, in the 4th period, the size does not decrease regularly<\/strong>. This irregularity is primarily due to the presence of the 3d orbitals<\/strong>:<\/p>\n\n\n\n
      \n
    • As 3d electrons are added (from Sc to Zn), they do not shield the nuclear charge effectively.<\/li>\n\n\n\n
    • This leads to only a slight decrease or near constant atomic radii<\/strong> across the transition metals.<\/li>\n\n\n\n
    • After Zn, the size starts decreasing more noticeably again with p-block elements (Ga to Kr).<\/li>\n<\/ul>\n\n\n\n
      \n\n\n\n
      Trend of Ionization Energy in a Period<\/h3>\n\n\n\n
      Ionization energy (IE)<\/strong> is the energy required to remove an electron from a neutral atom in its gaseous state.<\/p>\n\n\n\n
        \n
      • Trend:<\/strong> Ionization energy generally increases across a period<\/strong> from left to right.<\/li>\n\n\n\n
      • Reason:<\/strong> Increasing nuclear charge holds electrons more tightly.<\/li>\n\n\n\n
      • Exceptions:<\/strong> Slight dips occur, such as between Group 2 and Group 13<\/strong> and Group 15 and Group 16<\/strong>, due to sublevel electron configurations and electron repulsion effects.<\/li>\n<\/ul>\n\n\n\n
        In the 4th period, ionization energy increases overall from K to Kr, but with minor irregularities due to electron shielding and subshell stability.<\/p>\n\n\n\n
        \"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"
        Why and how are elements arranged in the 4th period? Why does the size of an atom not decrease regularly in a period? Give the trend of ionization energy in a period. The Correct Answer and Explanation is: Why and How Are Elements Arranged in the 4th Period? Elements in the 4th period of the […]<\/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-223866","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/223866","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=223866"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/223866\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=223866"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=223866"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=223866"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}