Chemistry Chapter 5 Study Guide

Periodic
Repeating patterns.

Periodic Law
The physical and chemical properties of the elements that are periodic functions of their atomic numbers.

Periodic Table
Arrangement of the elements by their properties.

Modern Periodic Table
Since Mendeleev… Elements arranged in order of atomic numbers so elements with similar properties are in the same group. Chemists have discovered many new elements and synthesized new elements. Noble Gases, Lanthanides and Actinides have been added.

Lanthanides (Rare Earths)
Atomic #’s 58-71. All very similar properties. They are shiny, reactive metals. Similar to the reactivity of alkaline earth metals. The electrons fill up the F orbitals.

Actinides
Atomic #’s 90-103. Extremely rare and all are synthesized except for 90-92. Radioactive metals.

Periods
The horizontal arrangement of elements on the periodic table. The length of it is determined by the number of electrons that can occupy the sub-levels being filled in that period.

s, p, d, and f blocks
Based on the electron configuration of elements. The blocks (or sub-levels) are used to tell what group an element will be in. The s block holds 2 electrons maximum, the p block holds 6, the d block holds 10, and the f block holds 14.

Alkali Metals
Group 1. Most reactive, soft, silvery metals. Stored under kerosene/oil. They are too reactive to exist in nature, but are found as compounds. Combine readily with non-metals and water.

Alkaline Earth Metals
Group 2. Similar to Alkali Metals, but are harder, denser, stronger, and have higher melting points. Less reactive than Alkali Metals, but still cannot be found in nature.

Transition Elements
Groups 3-12. The group number is the d+s electrons. They are shiny, conductors of heat and electricity, ductile and malleable. Less reactive than groups 1 and 2, and some can exist free in nature (native elements) because of how nonreactive they are.

Main Group Elements
Groups 13-18. Those elements occupying the s and p blocks of the periodic table. Minus group 1 and 2, they have the lowest electronegativities. (Properties vary: Metalloids – Brittle solids, semiconductors, exhibit properties of both nonmetals and metals. Mixture of metals, non-metals, and noble gases.)

Halogens
Group 17. Most reactive non-metals. When reacting with metals, form salts. F2 (green gas), Cl2 (yellow gas), Br2 (red liquid), I2 (purple solid).

Noble Gases
Group 18. Stable elements, do not normally undergo chemical reactions because they have full outer valence electron shells (the electrons fill the highest energy level). Helium is 1s^1 while the rest are called “stable octets” because they have 8 electrons in the outer energy level.

Ion
An atom or group of bonded atoms that has a positive or negative charge.

Ionization
Any process that results in the formation of an ion.

Cation
A positively charged ion.

Anion
A negatively charged ion.

Atomic Radii
One-half the distance between the nuclei of identical atoms that are bonded together.

Ionic Radii
One-half the distance the diameter of an atom’s ion. The sum of ionic radii of the cation and anion gives the distance between the ions in a crystal lattice.

Ionization Energy
The energy required to remove one electron from a neutral atom of an element.

Electron Affinity
The energy change that occurs when an electron is acquired by a neutral atom.

Electronegativity
A measure of the ability of an atom in a chemical compound to attract electrons.

Stanislao Cannizzaro
Introduced a method for accurately measuring the relative masses of atoms. Allowed for chemists to agree on standard values for atomic mass so that they could find the relationship between atomic mass and other properties of the elements.

Dmitri Mendeleev
Published the first periodic table by arranging the elements by their chemical and physical properties. He found that as the atomic masses go up, certain similarities in their chemical properties appeared at regular intervals. Predicted unknown elements which were later found with very similar properties to Dmitri’s predictions.

Henry Moseley
Realized that the elements were arranged in order of increasing nuclear charge (i.e., atomic number). He established the Periodic Law. He found that elements are arranged by increasing atomic number, no mass.

Group Configurations/Group Numbers
For groups 1 and 2, the number of valence electrons (the little exponent things [Ex: 1s^2 2s^2 2p^6 (the 2, 2, and 6)]) and the group number are the same. For groups 13 through 18, the number of valence electrons is the group number minus 10. For example, group 15 has 5 valence electrons because 15 – 10 = 5.

Valence Electrons
The electrons available in chemical compounds to be shared, gained, or lost.

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