Periodic Table, Atoms, and Bonding (Chapter 5)
Valence electrons are the electrons with the highest energy levels. Valence electrons determine the properties of that element and the ways it bonds with other elements.
Dot Diagrams show the arrangement of valence electrons. After the number of valence electrons reaches the stable number of eight, a new period begins. See Figure 4 pg. 179.
http://www.youtube.com/watch?v=y6QZRBIO0-o
The Periodic Table shows the structure of the atoms including the arrangement of the electrons in each element. Knowing the number of valence electrons helps determine how different elements will combine and react with one another.
Elements to the left of the dark zig-zag line are the metals. Elements to the right are the nonmetals.
Group 18, the inert gases, do not react with anything since there are a total of 8 valence electrons in each of the atoms of these elements.
The element’s atomic number increases by one from the left side to the right side. Group 1 (one valence electron) reacts violently with Group 17, (seven valence electrons), to make a stable number of eight valence electrons, ex. Sodium (Na+) and chlorine (Cl-). Sodium donates it’s electron to chlorine’s seven electrons making a stable eight electrons.
Ions are atoms or groups of atoms that have a charge.
Ionic bonds form as a result of the attraction between positive and negative ions. These are strong bonds and ionic compounds have high melting points. Ionic bonds form when a metal reacts with a nonmetal.
Ionic crystals are three dimensional arrangements and when melted in water they will conduct an electrical current.
A covalent bond is when two or more atoms share electrons.
Covalent bonds usually form between atoms of nonmetals.
The force that holds atoms together in a covalent bond is the attraction of each atom’s nucleus for the shared pair of electrons.
A molecule is a neutral group of atoms joined by covalent bonds.
Compared to ionic compounds, molecular compounds generally have lower melting points and boiling points. Unlike ionic compounds, molecular compounds do not conduct an electric current when melted or dissolved in water.
A covalent bond where the electrons are shared unequally is called a polar bond. A nonpolar bond is where the electrons are shared equally. (See figure 18 pg. 196.)
An alloy is a mixture made of two or more elements, at least one of which is a metal. Alloys are stronger and less reactive than the metals from which they are made.
Metal atoms combine in regular patterns in which the valence electrons are free to move from atom to atom. Metals are therefore malleable, have a high luster, (shiny), and can conduct heat and electricity well.
http://www.youtube.com/watch?v=SmwlzwGMMwc Element Song
https://www.youtube.com/watch?v=zUDDiWtFtEM&list=PLz4XX3F7wI3DCXkahI50X_V_JAik4ktot&index=6
Element Song (newer)
https://www.youtube.com/watch?v=O-48znAg7VE&list=PLz4XX3F7wI3DCXkahI50X_V_JAik4ktot&index=11
Periodic Table 4 minutes