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Periodic Trends

By Andrew T. and Austin R.

Austin Roberts

on 5 May 2011

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Transcript of Periodic Trends

Periodic Trends By Andrew T and Austin R


Prenzlauerberg Atomic Radius Atomic radius DECREASES ACROSS A PERIOD due to a stronger magnetic force from the increase in protons and electrons with the same degree of shielding.

Atomic radius INCREASES DOWN A FAMILY due to the increase in degree of shielding." Atomic Radius Trend "Atomic radius measures the overall size of the electronic density for an atom. Ionic Radius "Ionic radius measures the overall size of the electronic cloud for a charged element, or ion. Cation, or positively charged ions, have SMALLER RADII than their neutral atom. This is due to the GREATER ATTRACTION from the nucleus.

Anion, or negatively charged ions, have LARGER RADII than their neutral atom. This is due to greater electron to electron REPULSION." Ionization Energy (IE) "Ionization energy is the energy required to remove an electron from the valence shell, the highest energy level. MORE ENERGY is required for an electron to be removed from an atom due to the decreasing radius ACROSS A PERIOD.

This decrease in radii STRENGTHENS the ENC, which pulls the electrons CLOSER to the nucleus.

As you move DOWN A FAMILY, shielding increases thus decreasing the IE which weakens the ENC." Electronegativity (EN) "EN is the ability for an atom to "steal", or take electrons from a neighbouring substance. NOTE:
High EN: the atom CAN easily take electrons
Low EN: the atom CANNOT easily take electrons EN INCREASES across the period due to smaller radii from the INCREASED PULL from the protons.

EN DECREASES down the family due to larger radii from the INCREASED degree of shielding as you go down as well the DECREASED ENC.

The MOST electronegative family are the halogens, and the LEAST electronegative family are the alkali metals." Effective Nuclear Charge (ENC) "An ATTRACTIVE force that allows the electrons to orbit around and stay close to the nucleus.

The distance from the nucleus, and the shielding effect, the inner electrons weaken the pull from the nucleus for the valence electrons, are two factors that reduce the attraction between the valence electrons and the nucleus.

Effective Nuclear Charge is a central concept in this unit because there is a relationship between it and the following trends." "Good question Andrew, oxygen is the MORE REACTIVE atom than nitrogen. Even though nitrogen is closer to the alkali metals, the most reactive family, it has a half full p-orbital which makes it more stable than oxygen which has four electrons in its p-orbital. Thus making it less reactive." "Mr. Prenzlauerberg, which atom is more reactive, O or N?" "Umm, why is H found in virtually all molecules/compunds in our planet?" "Hydrogen is found in many molecules/compounds in our planet because it is very versatile in the sense that it can either give or take one electron to become stable. Thus being able to pair up with many other atoms. Also, there is no shielding as there is just the lone electron." "Hello class, my name is Professor Prenzlauerberg. Today I'm going to teach you about the trends on the periodic table." "Yes Michael, they are both considered precious metals since they are non reactive. Ag and Au are non-reactive because of the way their electrons are positioned. They can become stable by moving an electron from the s-orbital to the d-orbital. This leaves the s-orbital half full and the d-orbital fully full. On the board is the core notation showing how the orbitals change." Ag - [Kr] 5s2 4d9

Au - [Xe] 6s2 5d9 Ag - [Kr] 5s1 4d10

Au - [Xe] 6s1 5d10 "Sir, do electrons do anything before bonding, how do they prepare for it? "We already went over this Feras, but yes they do. When elements bond, they either share electrons or give/take them away. Before this bonding occurs, the electrons get "excited" and move around to get ready for the bond." "Fluorine has the HIGHEST IONIZATION ENERGY and ELECTRONEGATIVITY out of all the elements on the periodic table because it has very little shielding so the pull between the electrons and the protons is very strong, thus being able to "steal" electrons very easily since it only needs one more electron to be stable. This strong pull and weak shielding make Fluorine have the LOWEST ATOMIC RADIUS." "Francium has the LOWEST IONIZATION ENERGY and ELECTRONEGATIVITY out of all the elements on the periodic table because it has so much shielding thus making the pull between its protons and electrons very weak. This makes it very easy for other elements to steal it's one valence electron. This weak pull and abundance of shielding make Francium have the HIGHEST ATOMIC RADIUS." "Yo Prenz, why is gold and silver so expensive, are they precious or something?" "Alright class, we have 8 minutes left. Are there any questions you want me to go over?" "Okay great class today. Please don't forget your test next class on Periodicity. If you have any questions feel free to ask!" "There is an INVERSE RELATIONSHIP between atomic radius and ENC. As atomic radius INCREASES, ENC DECREASES."
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