Formulas
the percentage by mass of each element present in a chemical compound
percent composition
rows are called this
periods
Group 16
Chalcogens
the category of elements which always lose electrons when ionizing
metals
an atom that has either a positive or negative charge
ion
the lowest whole number ratio of elements in a compound
columns are called this
groups
Group 2
Alkaline Earth Metals
the category of elements that always gain electrons when ionizing
nonmetals
this category of elements can bond with almost any other element
nonmetals
actual number of atoms of each element in a compound
molecular formula
the scientist who came up with the first periodic table of the elements
Dmitri Mendeleev
Group 1
Alkali Metals
the category of elements which always usually resemble nonmetals, but which sometimes can conduct electricity (like metals)
metalloids
this group never ionizes or bonds with other elements
noble gases/group 18
dividing the element mass by the total mass and multiplying it by 100 gives us this
percent composition
The numbers labeling each period also represent:
the number of electron shells
Groups 3-12
Transition Metals
negative ions
anions
this category of elements never bonds with other elements in the same category
metals
to find molecular formula, you divide ____________________ by the ________________ to get a whole number
molecular mass, empirical formula mass
this group of elements wasn't included on the original periodic table
Group 17
Halogens
positive ions
cations
this element has 1 valence electron and although it usually loses an electron, it is also happy to gain an electron to fill its valence shell
hydrogen