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Chem - Vocabulary
Terms in this set (40)
a force that exists between charged particles of like or opposite charge
an attraction that pulls two atoms together and allows them to form new substances
If the two atoms have about equal pull on each other's electrons, they become closer until their atomic orbitals overlap. The two atoms form some combined orbitals and share electrons. In this situation, the atoms have formed a covalent bond.
Atoms in a covalent bond cannot move closer together because the repulsion forces become too great and push the atoms apart. They also do not move further apart because the repulsion forces become weaker, and the attraction forces pull the atoms together. In covalent bonding, the attraction and repulsion forces balance each other out. It takes energy to push the atoms further apart or closer together.
Consider two atoms moving closer to each other. If one of the two atoms has a much greater pull than the other, then that atom is likely to completely strip electrons off the other. This atom that strips the electron becomes a negatively charged ion, an anion. The atom that loses the electron becomes a positively charged ion, a cation.
This exchange of electrons is not the end of the story. When ions with opposing charges are in the same environment, they tend to arrange themselves in well-ordered structures. The attraction forces that hold ions together in this structure are ionic bonds.
Groups of metal atoms form a different type of bond called a metallic bond. Metal atoms tend to form well-ordered structures, like those formed by ions. In the case of metal atoms, however, the valence orbitals of each atom overlap and form one giant orbital. The valence electrons of each atom can move freely within this common orbital. Note that each atom keeps its inner orbitals and inner electrons; only the valence orbitals form the common orbital.
Metal keeps together by the forces of attraction between the free-moving valence electrons and the atomic nuclei.
Regardless of the type of bond that forms, bonds are made for a particular reason. They help lower the potential energy by achieving a balance between attractive and repulsive forces. This results in increased stability.
To be ductile means a material can be pulled into thin wires. Metals are generally ductile. Copper metal, for instance, is commonly used as electrical wire. Shaping a metal into a wire is similar to flattening it into a sheet. When pulled, the shape of a metal changes. However, the electrons buffer the cations as they move. This keeps the crystal structure intact and the metallic bonds do not break.
However, if enough force is applied, a metal wire will break. This happens because the number of metallic bonds continually decreases as the metal wire thins out.
Luster refers to a shiny appearance. Metals generally have luster. When photons hit a metal surface, the electrons of the metal absorb some of them. This excites the electron, pushing it up to higher atomic orbitals. The electron is not stable at the higher atomic orbital and falls back to its ground level. As it does so, the electron releases energy as another photon. Thus, metals first absorb and then emit photons, creating shine.
When photons hit a metal surface, they may excite some electrons to higher atomic orbitals. If enough energy is provided to an electron, it will be knocked out entirely from the surface of the metal. Photons can actually knock electrons away from the metal completely. Thus, when light is shined on a metal surface, the surface will emit electrons. This phenomenon is called the photoelectric effect.
a bond formed through the attraction between oppositely charged ions
a grouping of cations and anions that has a zero net charge
representation that includes the symbols for all of the atoms present in a substance and shows the smallest whole-number ratios for the different atoms
single covalent bond
the sharing of two electrons (one electron pair) between two nonmetal atoms
double covalent bond
the sharing of four electrons (two electron pairs) between two nonmetal atoms
triple covalent bond
the sharing of six electrons (three electron pairs) between two nonmetal atoms
coordinate covalent bond
a bond where one of the nonmetal atoms contributes both electrons to the bond
a representation of a compound that uses round spheres for the atoms and long, thin rods for the bonds
representation of what a compound looks like in three-dimensional space that shows the physical overlap between the valence shells of the atoms
valence bond theory
a theory that states covalent bonds are formed from the overlap of atomic orbitals
-the distance between the nuclei of two bonded atoms
-For single bonds, the bond length is often close to the sum of the atomic radii of the two bonded atoms.
- the distribution of electron charge among two bonded atoms
- It is calculated from the difference in electronegativity of the two bonded atoms. Recall that electronegativity is a measure of an atom's ability to attract electrons in a bond. Consider the hydrogen fluoride (HF) molecule.
Now consider a bond between atoms of the same element, like a carbon-carbon (C-C) bond. In the C-C bond, both carbons have the same electronegativity. The shared electrons are not pulled toward either nuclei. The C-C bond is nonpolar. Nonpolar bonds happen between atoms with similar or equal electronegativity.
a molecule that has an uneven distribution of partial charges among its atoms
a molecule that does not have an uneven distribution of partial charges
representation of the fixed composition of a compound describing the elements and number of atoms of the element
compounds made of only two different elements
ions made of two or more atoms covalently bonded
What is an example of a cation and anion for a compound?
KCl (K1+ cation; Cl1- anion)
Using chemical nomenclature, what is the chemical name for K2S?
binary molecular compounds
molecular compounds that are composed of two different elements that are covalently bonded
a process that happens when one or more substances undergoes a chemical change to form new substances
chemical reactions that occur when one element within a compound is exchanged with another element
the SI unit in chemistry that represents the measure of a substance containing as many representative particles as atoms in exactly 12 grams of carbon-12
the mass of one mole of a substance
the volume of one mole of any gas at a specific temperature and pressure
the study of the quantitative relationships of the reactants and products in a chemical reaction
the amount of product that should be formed in a chemical reaction if all of the limiting reactant is completely consumed
the measured amount of product from a chemical reaction
the ratio of the actual yield compared to the theoretical yield of a chemical reaction, expressed in a percentage
law of definite proportion
scientific idea that states that different samples of a compound will possess the same defined proportions in that they have the same percentage of each element by weight or mass
law of multiple proportions
scientific idea that states that atoms of different elements combine in ratios of whole numbers to form a variety of different compounds
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