Chemistry Unit: Atom and Periodic Table Basics

A set of vocabulary flashcards covering the basic structure of the atom, properties of subatomic particles, and the organization of the periodic table groups.

Atom

The smallest unit of an element that has all of the properties of that element.

Proton

A subatomic particle with a positive charge found in the nucleus; the number of these determines the identity of an element.

Nucleus

The central region of an atom that contains the protons and neutrons.

Atomic Mass Unit (amu)

The unit of measurement for the mass of subatomic particles, where protons and neutrons each have a mass of $1\,amu$.

Electron

A subatomic particle with a negative charge found outside the nucleus in energy levels or shells.

Neutron

A subatomic particle with zero electrical charge found inside the nucleus of an atom.

Element

A substance made up entirely of one type of atom with an identical atomic number.

Atomic Number

The number of protons in an atom, which also equals the number of electrons in a neutral atom.

Chemical Symbol

A unique symbol of one or two letters for each element, always starting with a capital letter (e.g., $H$ for Hydrogen, $Fe$ for Iron).

Atomic Mass

The sum of the protons and the neutrons in an atom ($\text{protons} + \text{neutrons}$).

Isotopes

Atoms that have the same number of protons but different numbers of neutrons.

Groups (Families)

The $18$ vertical columns on the periodic table containing elements with similar properties.

Periods

The $7$ horizontal rows on the periodic table read from left to right.

Valence Electron

An electron found in the outer orbital of an atom that is responsible for making compounds and forming chemical bonds.

Alkali Metals

Group $1$ elements (excluding Hydrogen) that are the most reactive metals and are very soft.

Alkaline Earth Metals

Group $2$ elements that have $2$ valence electrons and are reactive, but less so than Group $1$.

Halogens

Group $17$ elements with $7$ valence electrons, known as the most reactive group of nonmetals.

Noble Gases

Group $18$ elements that are inert (stable) because they have a full outer electron shell ($8$ valence electrons, except Helium which has $2$).

Inert

A term describing elements that are stable and unreactive because they possess a full outer electron shell.