Quiz 1: Isotopes, Ions, and Average Atomic Mass 9th Grade Chem

Mass number

Total number of protons and neutrons in an atom.

Atomic number

The number of protons in an atom, found as the larger number on the periodic table.

Atomic mass

The average of the relative amounts of each isotope of an element.

Electrons

Negatively charged particles found outside of the nucleus of an atom.

Protons

Positively charged particles found in the nucleus of an atom.

Neutrons

Uncharged particles found in the nucleus of an atom.

Neutral atoms

Atoms that have the same number of electrons and protons.

Isotopes

Atoms of the same element with the same number of protons but a differing number of neutrons.

Ions

Atoms that have an unequal number of protons and electrons, resulting in a charge.

Positive ion

Formed when an atom has more protons than electrons.

Negative ion

Formed when an atom has more electrons than protons.

Fractional abundance

The percentage of a particular isotope in a total sample of atoms, expressed as a decimal.

Calculating average atomic mass (AAM) formula

(atomic mass of isotope #1) x (fractional abundance of isotope #1) + (atomic mass of isotope #2) x (fractional abundance of isotope #2).

Significant figures rule for multiplication/division

Round to the least number of significant figures in the calculation.

Significant figures rule for addition/subtraction

Align decimal points; round to the smallest number of decimal places.