Periodic Trends & the Periodic Table

Periodic Table Periodic Table – arrangement of elements in order of increasing atomic number with elements having similar properties in vertical columns Groups – vertical columns Periods – horizontal rows

Group Names Group Name 1A Alkali Metals 2A Alkaline Earth Metals Chalcogens Halogens Noble Gases

Groups Representative elements – group A elements Transition elements – group B elements Lanthanide and actinide series = inner transition metals

Groups The group tell you the number of valence electrons that the element has Valence electrons are electrons in the outermost shell of the atom All group 1A elements have 1 valence electron. Likewise, all group 8A elements have 8 valence electrons.

Octet rule The maximum number of electrons that the outer energy level can hold is 8. Valence shell = outer energy level All elements try to establish an outer energy level like the noble gases. They do this by gaining or losing electrons.

Oxidation numbers The charge an element would have if it released or obtained electrons to look like a noble gas. Metals release electrons Nonmetals obtain electrons

Predict the oxidation numbers for the following A. Al B. Mg C. N D. Na E. Cl

Characteristics Elements in the same group exhibit similar chemical characteristics due to the fact that they all have the same number of valence electrons. The most stable number of valence electrons is 8 This is called an octet

Charges Every element wants 8 valence electrons to become stable. They will gain or lose valence electrons to form an octet For example…Group 1A elements have 1 valence electron. They can either gain 7 electrons to have an octet or lose 1. What is easier? Lose 1 If an element loses 1 electron (1 negative charge) what charge will the resulting ion have? +1

Charges Let’s go to group 7A. This group has 7 valence electrons It can either loose 7 or gain 1 What is the easiest? Gain 1 What will be the resulting charge if the element gain 1 electron (1 negative charge)? -1

Physical States and Classes of the Elements The majority of the elements are metals. They occupy the entire left side and center of the periodic table. Nonmetals occupy the upper-right-hand corner. Metalloids are located along the boundary between metals and nonmetals

Metals Metals are elements that have luster, conduct heat and electricity, and usually bend without breaking.

Transition Metals The elements in Groups 3 through 12 of the periodic table are called the transition elements. All transition elements are metals. Many transition metals can have more than one charge

Inner Transition Metals In the periodic table, two series of elements, atomic numbers 58-71 and 90-103, are placed below the main body of the table. These elements are separated from the main table because putting them in their proper position would make the table very wide. The elements in these two series are known as the inner transition elements.

Inner Transition Metals The first series of inner transition elements is called the lanthanides because they follow element number 57, lanthanum. The second series of inner transition elements, the actinides, have atomic numbers ranging from 90 (thorium, Th) to 103 (lawrencium, Lr).

Non Metals Although the majority of the elements in the periodic table are metals, many nonmetals are abundant in nature Most nonmetals don’t conduct electricity, are much poorer conductors of heat than metals, and are brittle when solid. Many are gases at room temperature; those that are solids lack the luster of metals.

Properties of Metals and Nonmetals

Metalloids Metalloids have some chemical and physical properties of metals and other properties of nonmetals. In the periodic table, the metalloids lie along the border between metals and nonmetals.

Electron Dot Structures An electron dot structure consists of the elemental symbol surrounded by dots which represent valence electrons

Examples Draw the electron dot structure for Na Draw the electron dot structure for Al Draw the electron dot structure for Br

Periodic Trends Periodic Trends are trends that occur across the periodic table and down the periodic table They include: atomic radius, Ionization energy, electro negativity, metallic character, and ionic radius

Atomic Radius Atomic Radius – size of the atom  Decreases Increases 

Atomic radius The distance from the outer edge of the electron cloud to the nucleus. The radius increases as the principle quantum number increases. So elements increase going from top to bottom. The period they are in increased, radius increases.

As you move from left to right across the period things change. The # of protons in the nucleus increases. This causes the electrons to be attracted to the nucleus more and the size of the elements decrease. As you move from left to right radius decreases.

Which element in the pair is larger? A. Sn, Sr B. Cl, I C. S,P D. Ac, U E. Na, Rb F. B, Al

Determining the Atomic Radius of a Nonmetal (Chlorine) Click in this box to enter notes. Go to Slide Show View (press F5) to play the video or animation. (To exit, press Esc.) This media requires PowerPoint® 2000 (or newer) and the Macromedia Flash Player (7 or higher). [To delete this message, click inside the box, click the border of the box, and then press delete.] Copyright © Houghton Mifflin Company. All rights reserved.

Determining the Atomic Radius of a Metal (Molybdenum) Click in this box to enter notes. Go to Slide Show View (press F5) to play the video or animation. (To exit, press Esc.) This media requires PowerPoint® 2000 (or newer) and the Macromedia Flash Player (7 or higher). [To delete this message, click inside the box, click the border of the box, and then press delete.] Copyright © Houghton Mifflin Company. All rights reserved.

Ionization Energy Ionization energy – the ability to pull off 1 electron  Increases Decreases 

Ionization energy The energy required to remove the most loosely held electron from an element. Large radii elements lose electrons easily Small radii elements require energy to remove electrons.

Metals- don’t like electrons lose them easily Nonmetals – like electrons, want to keep them, require energy to remove them.

Electro negativity Electro negativity – the ability of an atom to attract another atom  Increases Decreases 

Metallic Character Metallic character – how much like a metal the element is  Decreases Increases 

Electron affinity The ability of an atom to attract electrons to itself. Metal = low affinity Nonmetals = high affinity Large radius = low affinity Small radius – high affinity

Metals and nonmetals Metals tend to lose electrons. Nonmetals tend to gain electrons. The goal is to get enough electrons in the outer energy level to look like a noble gas. Every electron lost leaves behind a net + charge.

Energy electron gained causes a net – charge. These charges effect the radius of the elements. Elements with charges are called ions

Ionic radius The more + charge and ion has the greater the ability to attract electrons to itself and is therefore smaller. The more – charge an ion has the more electrons it has pulling away from the nucleus and therefore they are larger.

Which is larger? A. Ca, Ca+2 B. F-, Cl- C. As-, P-3 D. Pb, Pb+4

Ionic Radius When you talk about ionic radius, you are comparing an atom and its ion When an atom has a negative charge, you have added electrons Which makes it bigger For example, which will be larger: Cl or Cl-1

Ionic Radius When an atom has a positive charge, you have taken away electrons Which makes it smaller For example, which will be larger: Na or Na+1

Periodic Table Trends Click in this box to enter notes. Go to Slide Show View (press F5) to play the video or animation. (To exit, press Esc.) This media requires PowerPoint® 2000 (or newer) and the Macromedia Flash Player (7 or higher). [To delete this message, click inside the box, click the border of the box, and then press delete.] Copyright © Houghton Mifflin Company. All rights reserved.

Ionic Radii Click in this box to enter notes. Go to Slide Show View (press F5) to play the video or animation. (To exit, press Esc.) This media requires PowerPoint® 2000 (or newer) and the Macromedia Flash Player (7 or higher). [To delete this message, click inside the box, click the border of the box, and then press delete.] Copyright © Houghton Mifflin Company. All rights reserved. Copyright © Houghton Mifflin Company. All rights reserved.