Activity Periodic Trends

ACTIVITY: Periodic Trends This activity will provide an opportunity to examine the periodic table more closely. Use the interactive periodic table (see link below) to explore trends of atomic radius, ionization energy, and electronegativity across a period and down a group on the periodic table. Part 1 – Atomic Radius: (click on radius / calculated radius in the options in the middle of the screen) 1) Define atomic radius: (look up in your notes or text or online!) The atomic radius of an element is the distance between the nucleus and the edge of the electron cloud. 2) Examine the trend in atomic radius from left to right across a period by clicking on all the elements in the 2nd period. List their atomic radii below (pm = picometer or 1 x 10-12 m). Li , Be , B , C _ 67 pm _ , N _ 56 pm _, O _ 48 pm _, F _ 42 pm _, Ne _ 38 pm _ 3) What is the trend in atomic radius from left to right across a period? They start to decrease by a smaller number. The pattern of the number being subtracted from the radii within the 2nd period is 55, 25, 20, 11, 8, 6, and 4 4) Rationalize / explain this trend with respect to the nuclear attraction to the electron cloud. (look up in your notes or text or online if you need to!) Since more valence electrons are being added to the higher energy levels, the distance from the nucleus increases while the attraction decreases. 5) Examine the trend in atomic radius from top to bottom down a group by clicking on all the elements in the 1st group. List their atomic radii below (pm = picometer or 1 x 10-12 m). Li _ 167 pm _ , Na _ 190 pm _ , K , _ 243 pm _ , Rb _ 265 pm _ , Cs _ 298 pm _ , Fr _ Unknown _ 6) What is the trend in atomic radius from top to bottom down a group? The number is slowly increasing until the number is unreadable. 7) Rationalize / explain this trend with respect to the nuclear attraction to the electron cloud. (look up in your notes or text or online if you need to!) The electrons are not being added to the energy levels which causes the atom to obtain a stronger positive charge from the protons. This also causes a stronger pull on the electrons 8) Without looking at their atomic radii on the periodic table, try to organize the following elements in order of increasing atomic radius (Ge, He, Sr, O, Ba). *then check your answer using the ptable! Sr , Ba, Ge , O, He (Greatest to least) Part 2 – Ionization Energy: (click on ionization in the options in the middle of the screen) 1) Define ionization energy: (look up in your notes or text or online!) Ionization energy is the energy required to remove an electron from a gaseous atom or ion 2) Examine the trend in ionization energy from left to right across a period by clicking on all the elements in the 2nd period. List their 1st ionization energy below (kJ/mol is a unit of energy). Li _ 520.2 kJ/mol _, Be _ 899.5 kJ/ mol _, B , _ 800.6 kJ/mol _, C _ 1086.5 kJ/mol _, N _ 1402.3 kJ/mol_, O _ 1313.9 kJ/mol _, F _ 1681.0 kJ/mol _, Ne _ 2080.7 kJ/mol _ 3) What is the trend in 1st ionization energy from left to right across a period? The number is increasing as you move from left to right in the period. 4) Rationalize / explain this trend with respect to the nuclear attraction to the electron cloud. (look up in your notes or text or online if you need to!) Electrons become easier to remove due to the increasing distance from the nucleus and more energy levels. 5) Examine the trend in atomic radius from top to bottom down a group by clicking on all the elements in the 1st group. List their 1st ionization energy below (kJ/mol is a unit of energy). Li _ 520.2 kJ/mol _ , Na _ 495.8 kJ/mol _ , K , _ 418.8 kJ/mol _ , Rb _ 403.0 kJ/mol _ , Cs _ 375.7 kJ/mol _ , Fr _ 380 kJ/mol _ 6) What is the trend in 1st ionization energy from top to bottom down a group? The number is repeatedly going down and decreasing as you move down the group. 7) Rationalize / explain this trend with respect to the nuclear attraction to the electron cloud. (look up in your notes or text or online if you need to!) The electrons are not being added to the energy levels which causes the atom to obtain a stronger positive charge from the protons. This also causes a stronger pull on the electrons 8) Without looking at their 1st ionization on the periodic table, try to organize the following elements in order of decreasing 1st ionization energy (Cs, F, Se, P, Ga). *then check your answer using the ptable! Cs, Se, Ga, P, F (Least to greatest) 9) Click on Calcium. Use the sliding bar at the upper right corner of the periodic table to examine the 1st, 2nd, and 3rd ionization energies of calcium. Rationalize / explain the large jump in ionization energy from the 2nd to the 3rd ionization energy. The jump in the difference of energy is 3,766.6 Part 3 – Electronegativity: (click on electronegativity in the options in the middle of the screen) 1) Define electronegativity: (look up in your notes or text or online!) Electronegativity is a measure of how strongly atoms attract bonding electrons to themselves 2) examine the trend in electronegativity from left to right across a period by clicking on all the elements in the 2nd period. List their electronegativity below (this quantity is a relative scale without a unit). Li _ 0.98 _, Be _ 1.57 _ , B , _ 2.04 _, C _ 2.55 _, N _ 3.04 _, O _ 3.44 _, F _ 3.98 _, Ne _ Unknown _ 3) What is the trend in electronegativity from left to right across a period? The scale number increases slowly until it cannot be read anymore. 4) Rationalize / explain this trend with respect to the nuclear attraction to the electron cloud. (look up in your notes or text or online if you need to!) Electrons are being added to more energy levels and continue to move farther away from the nucleus. This causes the F.A. to decrease. 5) Examine the trend in electronegativity from top to bottom down a group by clicking on all the elements in the 1st group. List their electronegativity values below (this quantity is a relative scale without a unit). Li _ 0.98 _ , Na _ 0.93 _ , K , _ 0.82 _ , Rb _ 0.82 _ , Cs _ 0.79 _ , Fr _ 0.7 _ 6) What is the trend in electronegativity from top to bottom down a group? There is not a drastic change in the numbers as they continually decrease. 7) Rationalize / explain this trend with respect to the nuclear attraction to the electron cloud. (look up in your notes or text or online if you need to!) The electrons are again not being added to higher energy levels. 8) Without looking at their electronegativity on the periodic table, try to organize the following elements in order of increasing electronegativity: Ca, Li, C, As F. *then check your answer using the ptable! Li, Ca, As, C, F (Least to Greatest) 9) Provide an argument detailing why noble gases typically do NOT have electronegativity values. They don’t have electronegativity because they don’t form more compounds with other elements. They also aren’t on the pauling scale of electronegativity.