Ch 5 Section 1 Flashcards
Final noble gas Radon, was discovered in 1900 by
Friedrich Ernst dorn
Mendeleevs procedure left several
Empty spaces in his periodic table
In 1871, the Russian chemist boldly predicted the
Existence and properties of the elements that would fill the spaces
The success of mendeleevs predictions persuaded most chemists to accept his
Periodic table and earned him credit as the discoverer of the periodic law
Cannizzaros method enabled chemists to agree on
Standard values of atomic mass and initiated a search for relationships between atomic mass and other properties of the elements
Stanislao Cannizzaro presented a convincing method for accurately
Measuring the relative masses of atoms
Periodic law means that when the elements are arranged in order of increasing atomic number elements with
Similar properties appear at regular intervals
By 1860 more than… Elements had been..
60 discovered
Chemists had to learn the
Properties of these elements as well as those of the many compounds they formed
There was no method for accurately determine an elements
Atomic mass or the number of atoms of an element in a particular chemical compound
Different chemists used different atomic masses for the same elements resulting in
Different compositions being proposed for the same compounds
Cannizzaros method enabled chemists to agree on
Standard values of atomic mass and initiated a search for relationships between atomic mass and other properties of the elements
Mendeleev hoped to organize the elements according to their
Properties
Mendeleev noticed that when the elements were arranged in order of increasing atomic mass certain similarities in theirs
Chemical properties appeared at regular intervals. Such a repeating pattern is referrrrd to as periodic
Mendeleev created a table in which elements with similar properties were
Grouped together– a periodic table of the elements
Mendeleev placed iodine after tellurium although this contradicted the pattern of listing the elements in order of increasing atomic mass, if allowed Mendeleev to place tellurium in a group of elements with which it shares
Similar properties
Mendeleevs procedure left several
Empty spaces in his periodic table
Henry Moseley examined the
Spectra of 38 different metals
Moseley discovered a previously
Unrecognized pattern
Moseley found that the elements in the periodic table fit into patterns better when they were sat ranged in
Increasing order according to nuclear charge or the number of protons in the nucleus
Moseleys work led to both the modern definition of atomic number and the recognition that
Atomic number, not atomic mass, is the basis for the organization of the periodic table
Modeled discovery was consistent with mendeleevs ordering of the periodic table by
Properties rather than strictly by atomic mass
Today mendeleevs principle of chemical periodic is correctly stated in what is known as
The periodic law
Periodic law;: the physical and chemical properties of the elements are
Periodic functions of their atomic numbers
Periodic law means that when the elements are arranged in order of increasing atomic number elements with
Similar properties appear at regular intervals
The periodic table is an arrangement of the elements in order of their
Atomic numbers so that elements with similar properties fall in the same column or group
Perhaps the most significant addition to the periodic table came with the discovery of the
Noble gases
Strutt snd Ramsay discovered
Argon in 1894
Argon: a gas in the atmosphere that had previously
escaped notice because of its total all of chemical reactivity
In 1868, helium had been discovered as a component of the
Sun, based on the emission spectrum of sunlight
To fit helium and argon into the periodic table Ramsay proposed a
New group
Ramsay also discovered
Krypton and xenon
Final noble gas radon was discovered in 1900 by
Friedrich Ernst dorn
The lanthanides are the
14 events with atomic numbers from 58 to 71
Because lanthanides are so similar in chemical and physical properties the process of
Separation and identifying them was a tedious task
The actinides are rev
14 elements with atomic numbers from 90 to 103
Lanthanides and actinides belong to periods
6 and 7 respectively, between groups 3 and 4
Lanthanides and actinides are usually set off
Below main portion of periodic table to save space
Periodicity with respect to atomic number can be observed in
Any group of elements in the periodic table
The differences in atomic number between the group 1 metals follow the same pattern as the
Differences in atomic number between the noble gases
Starting with the first member of groups 13-17 a similar
Periodic pattern is repeated
The atomic number of each successive elements
8,18,18, and 32 higher than the atomic number of the element above it
The reason for periodic is explained by the arrangement of
The electrons around the nucleus
The atomic number of each successive element is
8, 18, 18, and 32 higher than the atomic number of the element above it
