Comp 2

element
substance with atoms that are all alike
compound
substance formed from two or more elements in which the exact combination and proportion of elements is always the same.
atom
the smallest particle of an element that still retains the properties of the element.
nucleus
positively charged center of an atom that contains protons and neutrons and is surrounded by a cloud of electrons.
proton
particle, composed of quarks, inside the nucleus of an atom that has a charge of +1.
neutron
neutral particle, composed of quarks, inside the nucleus of an atom.
electron
particle surrounding the center of an atom that has a charge of -1.
quark
particle of matter that makes up protons and neutrons.
electron cloud
area around the nucleus of an atom where the atom’s electrons are most likely to be found.
mass
amount of matter in an object.
atomic number
number of protons in an atom’s nucleus.
mass number
sum of the number of protons and neutrons in an atom’s nucleus.
isotope
atoms of the same element that have different numbers of neutrons.
average atomic mass
weighted-average mass of the mixture of an element’s isotopes
chemical property
any characteristic of a substance, such as flammability, that indicates whether it can undergo a certain chemical change.
periodic table
organized list of all known elements that are arranged by increasing atomic number and by changes in chemical and physical properties.
group
vertical column in the periodic table.
electron dot diagram
uses the symbol for an element and dots representing the number of electrons in the element’s outer energy level.
period
horizontal row in the periodic table

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