Chapter 4 CHEM

John Newlands

arranged the known elements according to their properties and in order of increasing atomic mass. he placed the elements in a table

Law of octaves

elements in a given row have similiar and physical properties which repeat every eight elements

Dimitri Mendeleev

produced the first orderly arrangement- Periodic table- of all 63 elements known at the time. he gave the symbol for each element along with all the chemical and physical properties as well as relative atomic mass. He left gaps in his periodic table and predicted the properties of missing elements. Also elements don’t always fit in neat order of atomic mass

Henry Moseley

studied x-ray spectra of 38 different elements and found out that the wavelengths of the lines in the spectra decreased in a regular manner as atomic mass increased . Essentially he gave the definition of the atomic number and showed that atomic number not mass was the basis of organization

periodic law

Mendeleev’s principle of chemical periodicity, states that the repeating physical and chemical properties of elements change periodically with their atomic number

valance electron

an electron that is found in the outermost shell of an atom and that determines the atoms chemical properties

a group

VERTICAL COLUMN of elements in the periodic table that share chemical properties

a period

HORIZONTAL ROW where elements have the same number of occupied energy levels

main group elements

an element in the s block or p block. Sometimes called representative elements because they have a wide range of properties

Alkali metals

elements in group 1. they react with water to make alkaline solutions. they have a single valance electron and therefore are very reactive. Because of their reactivity they are never found in nature as pure elements but combined with other elements to form compounds. These elements are soft and can be cut through with a knife. They are also good conductors of electricity.

Alkaline earth metals

elements in group 2. slightly less reactive then alkali metals. They have two VE and must loose both iin order to become stable and that takes more energy.

Halogens

elements in group 17. most reactive nonmetals because of their electron configuration. they have 7 VE- so one away from a full shell. when reacting they often gain one electron. They usually react with alkali metals since they only have one.

Noble gasses

elements in group 18. these elements have a full set of electrons in outermost shell making them stabel

Transition metals

groups 3-12, also known as d-block elements. they do no have identical outer electrons configuration.

Lanthanides

a member of the rare earth series of elements whos atomic number range from 58-71.

actinides

any of the elements of the actinide series which have atomic numbers from 89 through 103

a trend

a predictable change in a particular direction.There is a trend toward greater reactivity as you move down the alkali metals in group 1

Ionization energy

the energy required to remove an electron from an atom or ion. This energy tends to decrease as you move down a group. As you go down the elements has more occupied energy levels taking it further away from the nucleus

electron shielding

the reduction of the attractive force between a positively charged nucleus an its VE due to the cancellation of some of the positive charge by the negative charges of the inner electrons

horizontal ionization trends

ionization energy increases= low to high

vertical ionization trends

bottom to top= low to high

across

bottom left to top right= low to high

bond radius

half the distance from center to center of two like atoms that are bonded together

atomic radius trend

increases vertically going down

decreases going left to right.

Coulombs law

magnitude of force between two charged particles i s proportional to the charge of the first particles times the charge of the second divided by the distance squared

electronegativity

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

electronegativity trend

across a period= increase

down a group = decreases

ionic size

across a period= decreases

going down a period= increases

electron affinity

decreases going down

increases going across

ionic radii

increases going down

decreases going across