Student Resources

Overall

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  Metallic character refers to the level of reactivity of a metal to donate electrons during a chemical reaction.
  
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  Nonmetallic character relates to the tendency of an element to accept electrons during chemical reactions.
  
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  Metallic character increases going down a family group and decreases going across a period.
  
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  Nonmetallic character increases going from left to right across the periodic table and decreases going down a family group.
  

The following figure summarizes all of the major periodic trends within the periodic table

Figure 2.20 Summary of Major Periodic Trends
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2.10 Chapter Summary

Dalton’s Atomic Theory proposed that matter is made up of tiny particles called atoms that cannot be broken into smaller pieces. During a chemical reaction, atoms are rearranged, but they do not break apart, nor are they created or destroyed. An element is a substance that cannot be broken down into simpler chemical substances. There are about 90 naturally occurring elements known on Earth. The smallest unit of an element is the atom. All atoms of the same element are identical in mass and other properties, whereas atoms of different elements differ in mass and other properties.
The elements can be divided into three major classes: The metals, metalloids, and nonmetals. Metals are typically shiny, very dense, have high melting points, and are good conductors. Nonmetals are generally brittle, dull, have low melting points, and they are generally poor conductors. Metalloids have properties of both metals and nonmetals.
Dmitri Mendeleev organized the elements into a chart based on their similar characteristics and properties. Today this chart is known as the periodic table of the elements. Within the periodic table group, or family of elements, is a vertical column of the periodic table. Elements are placed into families due to their similar properties, characteristics, and reactivities. Group 1 elements are known as the alkali metals and are the most reactive elements of the metal class. Alkaline earth metals are found in group 2 and are almost as reactive as the group 1 metals. The transition metals are the larger block of elements extending from Groups 3-12 (also known as the group B elements). Transition metals have high melting points and boiling points, often form colored compounds that are highly stable, and they can serve as good catalysts. A catalyst is an agent that helps to speed up a chemical reaction without itself being changed in the process. Group 17 elements, known as halogens, contains very reactive nonmetals that often exist as diatomic elements (F2, Cl2, Br2, I2). Group 18 elements, the noble gases are extremely stable, unreactive, and rarely form compounds.
Atoms are made up of extremely small subatomic particles called protons, neutrons, and electrons. Protons (positively charged particles), and neutrons (electrically neutral particles) form the core or nucleus of an atom. Electrons are extremely small, negatively charged particles that form an electron cloud, which orbits the nucleus. The atomic number (Z) refers the the number of protons present in an element and is the defining feature of an element. The atomic mass (A) of an element is the sum of the protons and neutrons within that element.
Atoms of the same element (have the same atomic number) that have different numbers of neutrons are called isotopes. Most elements exist as isotopes. In fact, over 3,500 isotopes are known for the different elements. The atomic mass reported on the periodic table is the relative mass of the different isotopes of an element based on their abundance on the Earth. Some chemical elements can also form more than one type of structural lattice, these different structural lattices are known as allotropes. Allotropic changes affect how the atoms of the element interact with one another to form a 3-dimensional structure, but do not alter the sample with regard to the atomic isotope forms that are present, and do not alter or affect the atomic mass (A) of the element.
Understanding the electron configuration within an element is important for understanding the reactivity of the element. The modern theory of electron behavior is predicted by the field of quantum mechanics. The term quantum is defined as a discrete quantity or ‘packet’ of energy. Electrons in atoms can exist at different energy levels depending on how far away from the nucleus of that atom that they are positioned. Electrons typically have higher energy, the farther away they are (on average) from the nucleus. Four quantum numbers (n, l, ml, and ms) are used to assign the position of an electron within at atom. The principle quantum number (n) refers to the electron shells and corresponds to each period or row on the periodic table. The orbital angular momentum quantum number (l) refers to the electron subshell classification which can be of the s, p, d, or f categories. The magnetic quantum number (ml) refers to the electron orbitals, and the electronic spin number (ms) refers to the electron spin state of the electrons. Each orbital can house 2 electrons, each of which have an opposite spin. Each subshell can house a specific number of electron orbitals: s-subshells have one orbital and can house a total of 2 electrons, p-subshells have three obitals and can house a total of 6 electrons, d-subshells have five orbitals and can house a total of 10 electrons, and f-subshells have seven orbitals and can house a total of 14 electrons.
Electron orbitals are filled according to three major rules. The Pauli Exclusion Principle states that electrons cannot occupy the same space at the same time, and thus, no two electrons can share the same combination of four quantum numbers. Second according to the Aufbau principle, electrons orbiting one or more atoms will fill the lowest available energy levels before filling higher energy levels. The final rule that we need to follow is Hund’s rule which states that when electron orbitals have equal energy level, electrons must fill each of those orbitals as single electrons before they can begin to pair with electrons of opposite spin states. The periodic table and the electron configuration solitaire tool can be used to determine the electron configuration of any element. Electron configurations can be written using the noble gas shorthand rules.
The valence shell of an element is the outermost electron shell. The electrons housed within the valence shell are the most reactive electrons in an atom and are essential for forming chemical bonds with other elements. There are a total of eight electrons that can be housed in the valence shell of any atom. The periodic table can be used to predict the number of valence electrons present within an atom and electron dot symbols provide a graphic representation of the valence shell electrons.
Due to the organization of the periodic table according to proton and electron configurations, a number of interesting elemental trends can be observed. Atomic size, as measured by the atomic radius of an atom, increases and you move down a family group, and decreases as you move from left to right down a period or a row on the periodic table. The Electronegativity of an atom is the measure of an atom’s tendency to attract a bonding pair of electrons, and can be thought of as electron affinity. Electronegativity increases as you go from left to right across the periods of the periodic table and it tends to decrease as you move down family groups. Ionization energy is defined as the amount of energy required to remove the most loosely bound electron of an atom. Ionization energy tends to increase as you move across the periods of the periodic table from left to right, and decreases as you move down a family group. Metallic character refers to the level of reactivity of a metal, whereas nonmetallic character refers to the level of reactivity of nonmetals. The metallic character of the elements tends to go up as you move down a family group of elements and goes down as you move from left to right across a row of the periodic table. Concomitantly, nonmetallic character tends to go down as you move down a family group of elements and goes up as you move from the left to the right across the periodic table.

Video Tutorial of Electron Configurations and Ionization Energy By: Paul Anderson and Bozeman Science

 
 
 
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Homework Chapter 2

Part 1: Atomic Structure

 

2.11 References

Chapter 2 materials have been adapted and modified from the following creative commons resources unless otherwise noted:

1. Anonymous. (2012) Introduction to Chemistry: General, Organic, and Biological (V1.0). Published under Creative Commons by-nc-sa 3.0. Available at: http://2012books.lardbucket.org/books/introduction-to-chemistry-general-organic-and-biological/index.html
2. Poulsen, T. (2010) Introduction to Chemistry. Published under Creative Commons by-nc-sa 3.0. Available at: http://openedgroup.org/books/Chemistry.pdf
3. OpenStax (2015) Atoms, Isotopes, Ions, and Molecules: The Building Blocks. OpenStax CNX.Available at:  http://cnx.org/contents/be8818d0-2dba-4bf3-859a-737c25fb2c99@12.
4. LibreTexts (2017) Chem 121: Chapter 2 Atomic Structure. https://chem.libretexts.org/LibreTexts/Valley_City_State_University/Chem_121/Chapter_2%3A_Atomic_Structure/2.03%3A_Families_and_Periods_of_the_Periodic_Table
5. Robson, G.(2006) Wikipedia. https://en.wikipedia.org/wiki/Electron_shell
6. LibreTexts (2016) Physical and Theoretical Chemistry. https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Quantum_Mechanics/09._The_Hydrogen_Atom/Atomic_Theory/Electrons_in_Atoms/Electronic_Orbitals
7. High School Chemistry/Families on the Periodic Table. (2016) Wikibooks. https://en.wikibooks.org/wiki/High_School_Chemistry/Families_on_the_Periodic_Table#Alkali_Metals_Have_One_Electron_in_Their_Outer_Energy_Level
8. 1. Anonymous. (2012) Principles of General Chemistry (V1.0). Published under Creative Commons by-nc-sa 3.0. Available at: http://webmis.highland.cc.il.us/~jsullivan/principles-of-general-chemistry-v1.0/index.html
 
 

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  CH150: PREPARATORY CHEMISTRY
  
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  CH150: CHAPTER 1 – MEASUREMENTS IN CHEMISTRY
  
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  CH150: CHAPTER 2 – ATOMS AND PERIODIC TABLE
  
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  CH150: CHAPTER 3 – IONS AND IONIC COMPOUNDS
  
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  CH150: CHAPTER 4 – COVALENT BONDS AND MOLECULAR COMPOUNDS
  
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  CH150: CHAPTER 5 – CHEMICAL REACTIONS
  
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  CH150: CHAPTER 6 – QUANTITIES IN CHEMISTRY
  
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  CH150: CHAPTER 7 – SOLUTIONS