23 C 1.V.2 Modeling Atoms Vocabulary

group

a column running up and down the periodic table, with similar chemical properties

atomic mass unit (amu)

a mass equal to 1/12 the mass of a carbon-12 atom, and used as an equivalent to a proton or neutron

parentheses

a pair of round brackets used to mark off an inserted word or phrase(or set of chemical symbols to be multiplied)

period

a row running left to right across the periodic table, with no connected properties

chemical formula

a set of chemical symbols and sometimes subscripts and parentheses, showing the elements present in a compound and their relative proportions

average atomic mass

a weighted average of the masses of all the isotopes of the same element

periodic table

an arrangement of elements separated into groups based on a set of repeating properties

reference isotope

an isotope whose mass can be measured accurately and is used as the basis for a scale to compare the masses of other atoms

isotopes

atoms that have the same number of protons but different numbers of neutrons

natural percent abundance

how commonly an isotope occurs on Earth compared to other isotopes of the same element

electrons

negatively charged subatomic particles, which surround the nucleus

chemical symbol

one or two letters representing an element, with the first letter capitalized

protons

positively charged subatomic particles, located in the nucleus

superscript

smaller text written or printed above the normal line of type

subscript

smaller text written or printed below the normal line of type

neutrons

subatomic particles with no charge, located in the nucleus

nucleus

the dense central core of the atom, made up of positive and neutral particles

electron cloud

the disperse, almost empty area surrounding the nucleus where negative particles might be located

atomic number

the number of protons in the nucleus, which makes one element different from another

mass number

the total number of protons and neutrons added together in an atom