organizing the elements organizing the elements chapter 4 section 2
Post on 12-Jan-2016
226 Views
Preview:
TRANSCRIPT
Organizing the Elements Chapter 4 Section 2
Mendeleev
Russian scientist that discovered a set of patterns that applied to all the elements in 1869
Some elements have similar chemical and physical properties
Atomic mass is the average mass of all the isotopes of an element
He noticed that a pattern of properties appeared when he arranged the elements in order of increasing atomic mass
When Mendeleev arranged the 63 known elements by their atomic mass and arranged them into groups with similar properties, he had three blanks, which he correctly assumed were elements not discovered yet, and he even predicted some of their properties.
◦He published the first periodic table in 1869. A chart of elements showing the
repeating pattern of their properties
Period is a row in the table
Family(group) is a column in the table
Table arranged by atomic number today
Organization of the Periodic Table
The properties of an element can be predicted from its location of the periodic table.
Arranged by increasing atomic number
PeriodsHorizontal rows (7) that
contain a series of different elements
The properties of the elements change as you go from left to right (eg) elements on the left side are highly radioactive metals, less radioactive in the middle, and then the metalloids, followed by the nonmetals on the right.
The above pattern is repeated for each of the periods
Families
18 vertical columns
Consists of elements with similar chemical properties
Note: the actinide and lanthanide series are not part of the families and periods
Reading an Element’s SquareEach square includes the element’s
atomic number, chemical symbol, name, and atomic mass
A symbol is a shorthand way to write the element’s name. It consists of a capital letter, a Capital letter and a lower case letter, or a Capital letter and two lower case letters
Elements names can be in any language, but most are either in Latin, English, or Russian
The atomic mass is an average because most elements have isotopes of varying atomic masses
How elements form in the sun
The current theory is that all the elements discovered so far originally came from electrons that have escaped from stars.
Stars are made up of hydrogen, which is at high temperature and pressure. At this high temperature and pressure, Hydrogen exists as plasma ( a gas like mixture of free electrons and nuclei of atoms that have been stripped of electrons). Plasma has a positive charge, but the since the pressure and temperature is so great the particles do not repel each other.
FusionWhen colliding nuclei have enough
energy , they can join together.
Two small nuclei collide and fuse, forming a nucleus with a higher atomic number. Two larger nuclei then collide and fuse, forming a still larger nuclei and smaller nuclei which are released.
top related