Holt McDougal Chemistry Chapter 5

First International Congress of Chemists

Assembly of chemists in Karlsruhe, Germany with the aim of settling the issue of atomic mass as well as some other things that made communication difficult in relation to the elements.

Stanislao Cannizzaro

Italian chemist who presented a convincing method for accurately measuring the relative masses of atoms. This, in turn, enabled chemists to agree on standard values for atomic mass and initiated a search for relationships between atomic mass and other elemental properties.

Dmitri Mendeleev

Russian chemist who organized the elements in terms of increasing atomic mass; noticed certain similarities in their chemical properties appeared at regular intervals.

Periodic

Repeating pattern in which similarities occur at regular intervals.

Accurate

Mendeleev’s periodic table had several empty spaces. He predicted the existence and properties of elements that would fill three of the spaces. Were his predictions accurate or inaccurate?

Dmitri Mendeleev

Credited as the discoverer of periodic law.

Henry Moseley

English chemist who arranged the elements in order of increasing atomic number (nuclear charge), which made much more sense; elements with similar properties appeared at regular intervals. His work led to the modern definition of atomic number and the recognition that atomic number is the basis for organization of the periodic table.

Periodic Law

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

Periodic Table

An arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column, or group.

John William Strutt

English physicist who helped discover argon, an atmospheric gas with a total lack of chemical reactivity.

Sir William Ramsay

Scottish chemist who helped discover argon, helium (in the sun), krypton, and xenon. Proposed a new group in the Periodic Table called the Noble Gases, which would appear between Group 17 and Group 1.

Friedrich Ernst Dorn

German scientist who discovered radon, the final noble gas.

Periodicity

The idea that the differences between successive atomic numbers down a group follow the same or similar pattern in many groups.

Electron Configurations

The Noble Gases are so stable because of their _______________ _______________. Helium’s highest-occupied energy level (1s) is completely filled, and the rest have stable octets in theirs.

Highest-Occupied Energy Level

Generally, the electron configuration of an atom’s ___________-_____________ ________ ________ governs its chemical properties.

Groups

Vertical columns of elements that share similar chemical properties.

Periods

Horizontal rows of elements in which the length of each is determined by the number of electrons that occupy the sublevels being filled in that row.

S-Block

Elements of this block are chemically reactive metals.

Alkali Metals

The elements of Group 1 of the Periodic Table; extremely reactive because of the ease at which the single s electron is lost. They are silvery in appearance and soft enough to cut with a knife in their pure state, though they are not often found in one. Includes Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium.

Alkaline-Earth Metals

The elements of Group 2 of the Periodic Table; too reactive to be found in nature as pure elements, but they are still less reactive than their neighbors in Group 1. They are harder, denser, and stronger than Group 1 metals. Includes Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium.

There is an Empty Available P Sublevel

Why do the Group 2 metals have no special stability?

Hydrogen

Unique element with properties that do not closely resemble those of any group.

Helium

Although it has an electron configuration fit for Group 2, this element appears above Group 18 because of its special chemical stability.

Transition Elements

Elements in the d-block with typical metallic properties; they are good conductors of electricity and have a high luster. They are typically less reactive than elements of Groups 1 and 2, so much so that they can exist in nature as pure elements; Palladium, Platinum, and Gold are among the least reactive. Some deviations occur from orderly d sublevel filling however.

P-Block

Consists of all the elements of Groups 13-18, excluding helium. The total number of electrons in the highest-occupied energy level is equal to the group number minus 10. The properties of elements in this block vary greatly

Main-Group Elements

The s-block elements combined with the p-block elements.

Halogens

The elements of Group 17; they are the most reactive nonmetals because of the presence of 7 electrons in their outermost energy levels (one electron short of a noble-gas configuration). They react vigorously with most metals to form salts. Includes Fluorine, Chlorine, Bromine, Iodine, and Astatine.

Metalloids

Also known as semiconducting elements. They are located between nonmetals and metals in the p-block. They are mostly brittle solids with some properties of metals and some of nonmetals; their conductivity is in between the two.

P-Block Metals

Generally harder and denser than metals of the s-block, but softer and less dense than those of the d-block. They are often sufficiently reactive enough to not be found in nature as pure elements, but are stable in the presence of air once obtained as free metals.

Lanthanides

The 14 elements in Period 6 between those of Groups 3 and 4. Very similar in chemical and physical properties. They are shiny metals similar in reactivity to the Group 2 elements.

Actinides

The 14 elements in Period 7 between the elements of Groups 3 and 4. They are all radioactive. The first four have been found naturally on Earth, and the rest are known only as laboratory-made elements.

Atomic Radius

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

Left; Down

Atomic radius increases _______ and _______ on the Periodic Table.

The Increasing Positive Charge of the Nucleus

Why does atomic radius generally decrease across a period?

Electrons Occupy Main Energy Levels Farther From the Nucleus

Why does atomic radius generally increase down a group?

Ion

Atom or group of bonded atoms that has a positive or negative charge.

Ionization

Any process that results in the formation of an ion.

First Ionization Energy

The energy required to remove one electron from a neutral atom. A + energy = A^+ + e^-.

Up; Right

First ionization energy increases ________ and ________ on the Periodic Table.

The Electrons are More Strongly Attracted to the Higher Nuclear Charge

Why does the first ionization energy generally increase across a period?

Electron Shielding

Why does the first ionization energy generally decrease down a group?

Electron Shielding

The idea that the more electrons that lie between the nucleus and the electrons in the highest-occupied energy levels, the less affected those outer electrons will be by the nuclear charge.

Okay

The second ionization energy is always higher than the first, the third is always higher than the second, etc.

Stronger

Each successive electron removed from an ion feels an increasingly ____________ effective nuclear charge.

Noble-Gas Configuration

A jump in ionization energy occurs when an ion assumed a _______-________ ___________________.

Electron Affinity

The energy change that occurs when an electron is acquired by a neutral atom. A + e^- = A^- + energy if energy is released (this happens most commonly) or A + e^- + energy = A^- if the atom is forced to gain an electron by the addition of energy.

(0)

If energy is absorbed in electron affinity, the quantity of said energy is represented by ____ because it is so difficult to determine with any accuracy.

Up; Right

Electron affinity becomes more negative ______ and ______ in the Periodic Table. It’s important to note that group trends are not as regular in electron affinity.

2, 12, 18

In general, which groups experience an absorption of energy as it relates to electron affinity?

Positive

Second electron affinities are all __________ because it is more difficult to add an electron to an already negatively-charged ion.

Cation

Positive Ion. Formation of one leads to a decrease in atomic radius.

Anion

Negative Ion. Formation of one leads to an increase in atomic radius.

Decrease; Decrease

Cationic radii __________ across a period, and anionic radii __________ across each period for the elements in Groups 15-18.

Ionic Radius

There is a gradual increase in this down a group just as there is a gradual increase in atomic radius down a group.

Valence Electrons

The electrons available to be lost, gained, or shared in the formation of chemical compounds. Often located in incompletely-filled main-energy levels.

S; P

For the main-group elements, the valence electrons are those in the outermost ___ and ___ sublevels.

Linus Pauling

American chemist who devised a scale of numerical values reflecting the tendency of an atom to attract electrons.

Electronegativity

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

Fluorine

Element with the highest electronegativity (4), meaning it attracts electrons most strongly.

Up; Right

Electronegativity increases ______ and ______ in the Periodic Table.

They Do Not Form Compounds

Why can’t the Noble Gases be assigned electronegativities?

High

When a Noble Gas does form a compound, is its electronegativity high or low?

Less; Less

The properties of the d-block elements vary ______ and with ______ regularity than those of the main-group elements.