{"id":24823,"date":"2025-06-18T18:23:00","date_gmt":"2025-06-18T18:23:00","guid":{"rendered":"https:\/\/gaviki.com\/blog\/?p=24823"},"modified":"2025-06-18T18:23:02","modified_gmt":"2025-06-18T18:23:02","slug":"what-is-the-name-of-the-covalent-compound-pcl5","status":"publish","type":"post","link":"https:\/\/gaviki.com\/blog\/what-is-the-name-of-the-covalent-compound-pcl5\/","title":{"rendered":"What is the name of the covalent compound PCl5"},"content":{"rendered":"\n<p>What is the name of the covalent compound PCl5? I typed in phosphorous pentachloride but on Mastering Chemistry it says that is wrong.<\/p>\n\n\n\n<p><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-vivid-cyan-blue-color\"><strong>The correct answer and explanation is:<\/strong><\/mark><\/p>\n\n\n\n<p>The correct name of the covalent compound <strong>PCl\u2085<\/strong> is <strong>phosphorus pentachloride<\/strong>, <em>not<\/em> &#8220;phosphorous pentachloride.&#8221;<\/p>\n\n\n\n<p>The reason <strong>&#8220;phosphorus&#8221;<\/strong> is correct and <strong>&#8220;phosphorous&#8221;<\/strong> is wrong lies in the <strong>difference between elemental names and oxidation state naming conventions.<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">\ud83d\udd39 Explanation:<\/h3>\n\n\n\n<p>In naming <strong>binary covalent compounds<\/strong> (those made of two nonmetals), we follow the IUPAC system:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>The first element<\/strong> keeps its elemental name (like carbon, nitrogen, sulfur, or in this case, <strong>phosphorus<\/strong>).<\/li>\n\n\n\n<li><strong>The second element<\/strong> is named as if it were an anion: root name + <strong>-ide<\/strong> (e.g., chloride for Cl).<\/li>\n\n\n\n<li>Prefixes (mono-, di-, tri-, tetra-, penta-, etc.) are used to show how many atoms of each element are present.<\/li>\n<\/ol>\n\n\n\n<p>So for <strong>PCl\u2085<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The first element is phosphorus (no prefix because it\u2019s only one atom and it&#8217;s the first element).<\/li>\n\n\n\n<li>The second is chlorine, but since there are 5 atoms of chlorine, it becomes <strong>pentachloride<\/strong>.<\/li>\n<\/ul>\n\n\n\n<p>Putting it together:<br>\u2705 <strong>Phosphorus pentachloride<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">\u26a0\ufe0f Why \u201cPhosphorous\u201d Is Wrong:<\/h3>\n\n\n\n<p>&#8220;<strong>Phosphorous<\/strong>&#8221; (ending in <strong>-ous<\/strong>) is used in <strong>older naming systems<\/strong> (Stock system) to refer to <strong>a lower oxidation state<\/strong> of phosphorus (usually +3), as in <strong>phosphorous acid (H\u2083PO\u2083)<\/strong>.<br>On the other hand, <strong>\u201cphosphoric\u201d<\/strong> acid (H\u2083PO\u2084) refers to the +5 oxidation state.<\/p>\n\n\n\n<p>In <strong>PCl\u2085<\/strong>, phosphorus has an oxidation state of <strong>+5<\/strong>, not +3. But even then, for binary covalent compounds, we <strong>do not<\/strong> use &#8220;phosphorous&#8221; or &#8220;phosphoric&#8221; \u2014 we stick to the <strong>elemental name<\/strong>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">\u2705 Summary:<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Correct name<\/strong>: <strong>Phosphorus pentachloride<\/strong><\/li>\n\n\n\n<li><strong>Incorrect<\/strong>: <em>Phosphorous pentachloride<\/em> (because &#8220;phosphorous&#8221; implies a different naming system and oxidation state)<\/li>\n<\/ul>\n\n\n\n<p>Always use the <strong>element name<\/strong> and prefixes for binary covalent compounds!<\/p>\n","protected":false},"excerpt":{"rendered":"<p>What is the name of the covalent compound PCl5? I typed in phosphorous pentachloride but on Mastering Chemistry it says that is wrong. The correct answer and explanation is: The correct name of the covalent compound PCl\u2085 is phosphorus pentachloride, not &#8220;phosphorous pentachloride.&#8221; The reason &#8220;phosphorus&#8221; is correct and &#8220;phosphorous&#8221; is wrong lies in the [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-24823","post","type-post","status-publish","format-standard","hentry","category-quiz-questions"],"_links":{"self":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/24823","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/comments?post=24823"}],"version-history":[{"count":1,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/24823\/revisions"}],"predecessor-version":[{"id":24827,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/24823\/revisions\/24827"}],"wp:attachment":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/media?parent=24823"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/categories?post=24823"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/tags?post=24823"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}