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61 terms

Science Grade 6, Elements and Compounds

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elements
pure substances that cannon be broken down into any simpler substances.
lead
composed of the element carbon
water
composed of the elements hydrogen and oxygen. this is an example of a compound.
H2O
This means two parts hydrogen
compound
a sustance formed from the chemical combination of two or more elements.
Aristotle
A Greek philosopher who believed all things on Earth were made of four elements: air, earth, fire and water.
Au
Symbol for the element: Gold
Fe
Symbol for the element: Iron
S
Symbol for the element: Sulfur
Cu
Symbol for the element: Copper
C
Symbol for the element: Carbon
Al
Symbol for the element: Aluminum
He
Symbol for the element: Helium
six elements making up most of the human body
oxygen, carbon, hydogren, nitrogen, calcium, phosphorus
number of elements
about 100
atom
the smallest particle of an element that still has the same chemical properties of the elements.
number of atoms that fit in a space as small as the dot of a letter
millions
Democritus
Greek philosopher that believed matter could be cut into smaller and smaller peices only up to a certain point.
John Dalton
formulated the atomic theory.
atomic theory
matter must be made of tiny particles with spaces between them.
high powered microscope
this is needed to see atoms
atoms
these are mostly empty space
Rutherford experiments
These fired helium atoms at gold foil and found most went through the foil, some bounced back.
nucleus
the center of the atom which contains most of the mass
protons and neutrons
these are the two parts of the nucleus.
neutrons
these have no electrical charge, they are neutral.
protons
these have a positive electrical charge.
atomic number
the number of protons in an atom of an element.
atomic mass
the number of protons added to the number of neutrons.
different number of neutrons
atoms of the same element may have different numbers of these.
isotopes
atoms of the same element that have different atomic masses
electrons
these have a very small mass and a negative electrical charge.
these two parts of the atom have about the same mass
neutrons and protons
number of electronics in an atom
this does not change an atom's atomic number. they have virtually no mass.
these move around the nucleus
electrons
atoms generally have the same number of there
electrons and protons
ion
atom that has a positive or negative charge.
periodic table
a chart which shows the elements in the order of increasing atomic number. It is organized by a) physical properties and b) the number of protons
Dmitri Mendeleev
Russian chemist who developed a periodic table of the chemical elements.
periodic
this work means a repeating pattern.
groups or families
these are the vertical columns of the periodic table
periods
these are the rows of the periodic table.
different groups of elements
metals, nonmetals and metalloids.
metals
these conduct heat and electricity, become shiny when polished, melt at high temperatures and can be easily reshaped.
nonmetals
these have a dull surface, melt at lower temperatures and tend to break when bent.
metalloids
these have some properties of metals and some of nonmetals.
found as combinations of one of more elements
most elements exist in this manner.
shells of bird eggs
contains calcium, carbon and oxygen (Ca, C, O).
citric acid
contains carbon, hydrogen and oxygen (C, H, O).
table salt
contains sodium and chlorine (Na, Cl). Good example of a compound whose properties are quite different from the elements comprising the compound.
chemical formula
a simple way to indicate the composition of elements in a compound.
NaCl
chemical formula for sodium chloride.
CO2
chemical formula for carbon dioxide. Two parts oxygen for one part carbon.
A chemical formula showing compound with elements in a 1-to-1 ratio. It is held together by their opposite charges.
NaCl
A chemical formula showing compound with elements not in a 1-to-1 ratio
CO2.
molecule
the smallest particle of a compound that still has all the qualities of that compound. Their atoms are so tightly bonded that they act like a single particle.
H2
Hydrogen gas can exist as these types of molecules where two hydrogen atoms join together.
Water
H2O
Water molecules
oxygen shares its electrons with hydrogen and this joins the atoms together.
physical properties / number of protons
The factors used to organize the periodic table.
matter
this can be broken down into molecules, elements and atoms.