Atomic structure

Bohr, Niels

-electrons in specific paths/orbits -energy levels: electron absorbs energy - higher orbit electron loses energy - lower orbit and emits light

Rutherford, Lord Ernest

-electrons revolving around a heavy positive nucleus - cathode rays - electrons

electron

-one of the three fundamental units of and atom. -orbits around the nucleus of an atom and has very little mass. -has negative electrical charge

Neutron

-present in all elements except hydrogen -Neutral particle in nucleus. -Provides stability to nucleus -same atomic mass as protons but have a neutral electrical charge.

electron shell / energy level

-the orbit of and electron that surrounds the nucleus of and atom. -there can be seven electrons shells around an atom

Electron

Negatively charged particle orbiting the nucleus. Same number as protons in neutral atoms

radioactivity

a general term for the processes by which atoms with unstable nuclei radiate excess energy in the form of particles and energy.

atomic number

the number of protons in and atom

radioactive decay

the process by which radionuclides(radioactive atoms) emit particles and energy.

atomic mass

total mass of and atom measured by the mass of protons, neutrons, and electrons.

Dalton, John

-Elements classified by mass -atoms of an element were all the same.

Proton

-Positively charged particle in the nucleus. -Determines the atomic number or 'Z' number. -Present in the nuclei of all atoms

Thomson, Sir Joseph

Existence of a negative particle - electron. negative charges = positive charges - neutral atom

Noble gas

a gas that does not easily react with other elements to form a compound.

inert gas

a gas that is not know to bond with other elements to form a compound

Period

a quality of elements in the periodic table. Atoms in each period have at the same number of electron shells. There are seven periods that correspond to the seven electron shells.

Negative ion

an atom that has an extra electron and therefore a negative charge

stable atom

an atom that has the same number of protons and electrons

positive ion

an atom that is short one electron and therefore has a positive charge because of the unpaired proton.

radioactive element

and element composed of atoms with unstable nuclei that radiates particles and energy.

Isotopes

atoms that have the same number of protons but a different number of neutrons.

atomic group

grouping in the periodic table of the elements that is determined by the number of electrons in the outermost electron shell of the atoms in each element.

atom

made up of three fundamental particles: proton, neutron and electron

atomic mass number

number of protons plus the number of neutrons in the nucleus. "A" number

Periodic table of the elements

shows the atomic number and the atomic mass of all the elements arranged in and orderly way.

nucleus

the center of an atom: it consist of at least one proton. All elements except hydrogen have a nucleus that includes neurons.

strong nuclear force

the force of attraction b/w all the particles of a nucleus, both protons and neurons.