Elements & Atoms. What is chemistry?. Chemistry is the study of matter and its interactions. Matter is anything that has volume (takes up space) and has mass (weight). All matter is made of atoms Atoms are the building blocks of matter, sort of how bricks are the building blocks of houses.
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Elements & Atoms
AMU = Atomic Mass Unit; an incredibly small unit of mass created only to describe the mass of atoms and their particles
Information & picture from Chem4kids at http://www.chem4kids.com/files/atom_structure.html
Atomic Number 17
Mass Number 35
Number of protons:
Number of nuetrons:
Number of electrons
Number of Protons
Number of Nuetrons
Number of Electrons
Mass Number – Atomic Number
Same as the number of protons
The symbol of the element
Number of protons + neutrons.
Graphic from http://education.jlab.org/atomtour/fact2.html
Metalloids are located on the staircase line, dividing metals from non metals.
Have a mixture of metallic and nonmetallic properties.
Semi-conductors: Can conduct heat and electricity to some extent.
Columns of elements are called groups or families.
Elements in each group have similar but not identical properties.
For example, lithium (Li), sodium (Na), potassium (K), and other members of group 1 are all soft, white, shiny metals. (not H)
All elements in a group have the same number of outermost electrons.
Each horizontal row of elements is called a period.
The elements in a period are not alike in properties.
In fact, the properties change greatly across every given row.
The first element in a period is always an extremely active solid. The last element in a period, is always an inactive gas.
Elements in a period have the same number of energy levels.
1st Energy Level
2nd Energy Level
3rd Energy Level
Mass # = 7
Another way to represent the isotope is by