Chapter 8: Periodicity Flashcards
<p>What are S block elements</p>
<ul> <li>Elements that have their highest energy electron in the s orbitals</li></ul>
<p>What is a group</p>
<ul> <li>Is a vertical column of elements</li> <li>Elements in the same group have similar properties</li> <li>Same number of electrons in the outer shell</li></ul>
<p>Reactivity in Groups</p>
<ul> <li>Metals - get reactive going down the group</li> <li>Non-metals - get less reactive down the group</li> <li>Transition are unreactive</li> <li>Lanthanides are metalswhich are often not encountered, form 3+ ions in their compounds. Have similar reactivity</li> <li>Actinides are radioactive metals.</li></ul>
<p>What are periods</p>
<ul> <li>Horizontal rows in the periodic table are called periods</li> <li>There is a trend in physical properties and chemical behaviour across periods.</li></ul>
<p>What is the trend of periodicity of Group 3 elements explained by their electron arrangements</p>
<ul> <li>Sodium, Magnesium and Aluminium - Have giant structures. Lose electrons to form ionic compounds.</li> <li>Silicon, 4 electrons in the outer shell and forms 4 covalent bonds. Has some metallic properties classed as a semi metal.</li> <li>Phosphorous, Sulfur and chlorine - non metals. Either accept electrons to form ionic compounds or share electrons to form covalent compounds.</li> <li>Argon- full outer shell and is unreactive.</li></ul>
<p>What is the trend of melting and boiling points in Group 3</p>
<ul> <li>Sodium, Magnesium and Aluminium are metallic and GML <ul> <li>There is strong attraction between metal ions and delocalised electrons</li> <li>Al> Mg> Na : Higher charge, more delocalised electrons, smaller ions</li> </ul> </li> <li>Silicon - giant covalent - has to break many strong covalent bonds</li> <li>Phosphorous, Sulfur and Chlorine are simple covalent molecular: Weak van der waals between molecules. <ul> <li>S8 > P4 > Cl2 (bigger molecules, more electrons, more VDW)</li> </ul> </li> <li>Argon - Monoatomic SCM - very weak van der waals forces between atoms</li></ul>
<p>EXAM QUESTION: Identify the Period 3 element that has the highest melting point. Explain your answer by reference to structure and bonding.</p>
<ul> <li>Silicon has the highest melting point because it has a giant covalent structure</li> <li>and has many strong covalent bonds to break (covalent bonds need lots of energy to break)</li></ul>
<p>What is the trend of Atomic Radius across a period</p>
<ul> <li>Elements size decreases - becomes smaller <ul> <li>Outer electrons are in the same shell</li> <li>More protons in the nucleus</li> <li>Same amount of shielding</li> </ul> </li> <li>So stronger attraction between nucleus and outer shell electrons So outer shell electrons pulled closer to the nucleus</li></ul>
<p>What is the trend of Atomic Radius Down a group</p>
<ul> <li>Increases - gets bigger</li> <li>More shells (more energy levels)</li> <li>Increased amount of shielding</li> <li>Weaker attraction between nucleus and outer shell electron So outer electron further away</li></ul>
<p>What is first ionisation energy.</p>
<p>What is the trend of Ionisation Energies down a group</p>
<ul> <li>Is the energy required to remove1 mol of gasouselectrons from a mol of gaseous atoms to form 1+ ions.</li> <li>It decreases <ul> <li>More shells/ energy levels</li> <li>Greater distance between nucleus and outer electron</li> <li>Increased amount of shielding</li> </ul> </li> <li>So weaker attraction between nucleus and outer shell electrons So less energy required to remove one electron from the outer shell</li></ul>
<p>What is the general trend of Ionisation energies across a period</p>
<ul> <li>It increases</li> <li>More protons, increased charge</li> <li>Atoms get smaller</li> <li>Same shell/shielding</li> <li>Therefore stronger attraction from nucleus to electron in outer shell</li></ul>
<p>What are the 2 anomalies of the ionisation energies in a period</p>
<ul> <li>Group 2 - Group 3 <ul> <li>Electron lost from: Group 2 - s orbital Group 3 - p orbital.</li> <li>P orbital is higher energy than s orbital so easier to lose electrons</li> </ul> </li> <li>Group 5 - Group 6 <ul> <li>Group 5 elements loses electron from orbital with 1 electron</li> <li>Group 6 elements lose electrons from orbital with 2 electrons</li> <li>Extra electron- electron repulsions make it easier to lose an electronfrom p4 than p3</li> </ul> </li></ul>
<p>EXAM QUESTION: State and explain the general trend in first ionisation energies across a period</p>
<ul> <li>The general trend increases along the period.</li> <li>Greater nuclear charge/ more protons</li> <li>Same shielding. Electrons are added to the same shell.</li> <li>This shows that there is a stronger attraction from the nucleus to the outer electron</li></ul>
<p>Where is hydrogen and helium placed in the periodic table</p>
<ul> <li>Helium is usually placed above the noble gases because of its properties. It is not a p block element</li> <li>Hydrogen sometimes placed above Group 1 but on its own. Forms single charged +1 like group 1. However is a gas whilst group 1 are reactive metals. <ul> <li>Sometimes placed above halogens - it can form H- ions and bond covalently.</li> </ul> </li></ul>
<p>EXAM QUESTION: Give both examples which deviates from the general trend of first ionisation energies across period 3.</p>
<p>Explain why this deviation occurs.</p>
<ul> <li>Aluminum <ul> <li>Outer electron in 3p orbital/ sub shell (level)</li> <li>3p higher in energy - more shielded/ weaker nuclear attraction.</li> </ul> </li> <li>Sulfur <ul> <li>Outer electrons in 3p orbital begin to pair</li> <li>Repel</li> </ul> </li></ul>
