Unit 1 Part 1: Atomic Structure

Vocabulary flashcards covering subatomic particles, atomic regions, measurement units, atomic scale, and counting rules from Unit 1 Part 1: Atomic Structure.

Proton

A positively charged subatomic particle located in the nucleus with symbol $p^+$ , a charge of $1+$, a relative mass of $1\,\text{amu}$, and an actual mass of $1.673 \times 10^{-27}\,\text{kg}$ .

Neutron

A neutral subatomic particle located in the nucleus with symbol $n^0$, a charge of $0$, a relative mass of $1\,\text{amu}$, and an actual mass of $1.675 \times 10^{-27}\,\text{kg}$.

Electron

A negatively charged subatomic particle located in the electron cloud with symbol $e^-$, a charge of $1-$, a relative mass of $\frac{1}{1836}\,\text{amu}$, and an actual mass of $9.109 \times 10^{-31}\,\text{kg}$.

Atomic Mass Unit (amu)

A relative mass scale that compares every atom to a standard reference atom; $1\,\text{amu}$ equals $\frac{1}{12}$ the mass of one carbon-12 atom.

Carbon-12

The standard reference atom used for comparison in the atomic mass unit (amu) scale.

Nucleus

The central region of an atom containing protons and neutrons that has an overall positive charge and holds almost all of the atom's mass.

Electron Cloud

The region surrounding the nucleus that contains electrons, carries a negative charge, and holds almost all of the atom's volume.

Parts of the Atom Diagram

A schematic showing the dense nucleus containing protons and neutrons at the center, surrounded by negative electrons in motion within the electron cloud.

Overall Size of an Atom

The total diameter across an atom, which measures about $10^{-10}\,\text{m}$ across.

Relative Size of the Nucleus

The size of the nucleus relative to the electron cloud, which is $\frac{1}{100{,}000}$ of the electron cloud (analogous to a marble at the center of a stadium).

Atomic Number ($Z$)

The number of protons in an atom, which uniquely determines which element an atom is and equals the number of electrons in a neutral atom.

Mass Number ($A$)

The sum of the number of protons and neutrons in an atom.