Real Flashcards
IMPORTANT CONCEPT
To find the number of valence electrons in an atom of a representative element, simply look at its group number.
Electron Dot Structures
Diagrams that show valence electrons in the atoms of an element as dots.
Octet Rule
States that in forming compounds, atoms tend to achieve the electron configuration of a noble gas.
IMPORTANT CONCEPT
A positively charged ion, or a cation, is produced when an atom loses one or more of its valence electrons.
Metals most commonly produce cations
HOW DO TRANSITION METALS ACHEIVE STABILITY
Transition metals tend to form a pseudo-noble gas electron configuration. In saying pseudo-noble gas we mean that the transition metals generally “lose” the electrons in the highest energy level/orbital (which are usually not paired) in order for the highest energy level (and, thus every lower energy level) to be completely filled with electrons (which provides stability without achieving a noble gas config). Some elements may also have form pseudo-noble gas configs by losing the necessary amount of electrons in order for the highest energy shell to have its d-shell half-filled (which provides relative stability by way of Hund’s Rule).
IMPORTANT CONCEPT
An anion is produced when an atom gains one or more valence electrons; usually formed by nonmetals.
Halide Ions
The ions produced when atoms of chlorine and other halogens gain electrons.
Ionic Compound
A compound composed of cations and anions.
IMPORTANT CONCEPT
Although they are composed of cations and anions, ionic compounds are electrically neutral.
Ionic Bonds
The electrostatic forces that hold ions together in ionic compounds.
Chemical Formula
Shows the number of atoms of each element in the smallest representative unit of a substance.
Formula Unit
The lowest whole number ratio of ions in an ionic compound.
IMOORTANT CONCEPT
Most ionic compounds are crystalline solids at room temperature. Ionic compounds also generally have high melting points. They are nonconductive as solids, but do conduct electricity and heat if melted or dissolved in a solvent.
Coordination Number
The number of ions of opposite charge that surround the ion in a crystal
IMPORTANT CONCEPT
Ionic compounds can conduct electeicity when melted or dissolved in water. This is due to how the individual ions in an ionic compound dissociate when melted or dissolved in water. This dissociation allows for cations and anions to exist separately, which allows for a clear path for the flow of heat or electricity.
IMPORTANT CONCEPT
The valence electrons of atoms in a pure metal can be modeled as a “sea of electrons.” The valence electrons are mobile and can drift freely from one part of the metal to another. These mobile valence electrons prove as buffers in between the individual metal cations. Pure metals are ductile and malleable because, when force is applied to the metal, cations can slide past one another while still having valence electrons between them as buffers. Therefore, force can be applied to pure metals without them fracturing.
WHY DO IONIC COMPUNDS NOT HAVE THE PROPERTIES OF PURE METALS?
Due to the crystalline structure of ionic compounds, cations and anions are arranged in an alternate repeating pattern. Electrons in ionic compounds are not free to move, so the individual cations and anions remain rigidly in place. When force is applied, the cations and anions tend to be pushed closer together. When this occurs, anions repel the other anions and the cations repel the other cations. The repulsion results in the fracturing of the crystal and, thus, accounts for the brittleness of ionic compounds.
Alloys
Mixtures of two or more elements, at least one of which is a metal.
Why are alloys important?
Alloys are important because their properties are often superior to those of their component elements.
What are the most important alloys today?
Steels (carbon+iron).
Valence electrons
Electrons in the highest occupied energy level of an element’s atoms
