Elements and Atoms: The Building Blocks of Matter – Key Vocabulary

A set of vocabulary flashcards summarizing essential terms and definitions related to matter, elements, atomic structure, and the periodic table as presented in the lecture notes.

Matter

Anything that occupies space and has mass, existing as a solid, liquid, or gas.

Mass

The amount of matter contained in an object; constant regardless of location or gravity.

Weight

The measure of an object’s mass as affected by the pull of gravity; changes with gravitational strength.

Element

A pure substance that cannot be created or broken down by ordinary chemical means; 92 occur naturally.

Atom

The smallest unit of an element that retains that element’s unique chemical properties.

Subatomic Particle

Collective term for protons, neutrons, and electrons that make up an atom.

Proton

Positively charged subatomic particle located in the nucleus; defines an element’s atomic number.

Neutron

Neutral subatomic particle located in the nucleus; contributes to an atom’s mass number.

Electron

Negatively charged subatomic particle with very little mass that moves in the electron cloud around the nucleus.

Nucleus (atom)

Central region of an atom containing protons and neutrons.

Electron Cloud

Region surrounding the nucleus where electrons are likely to be found; electrons move erratically within it.

Atomic Number

The number of protons in the nucleus of an atom; uniquely identifies an element.

Mass Number

Whole number equal to the sum of protons and neutrons in a single atom’s nucleus.

Atomic Mass

Weighted average of the mass numbers of all naturally occurring isotopes of an element, expressed in amu.

Chemical Symbol

One- or two-letter abbreviation used to represent an element on the periodic table (e.g., Na for sodium).

Periodic Table of Elements

Reference chart arranging all known elements by atomic number and chemical properties.

CHON

Acronym for the four most abundant elements in the human body: Carbon, Hydrogen, Oxygen, Nitrogen.

Trace Elements

Elements required by the body in very small amounts (e.g., Fe, Zn, I); each makes up less than 0.1 % of body mass.

States of Matter

The three common physical forms—solid, liquid, gas—taken by substances depending on temperature and pressure.

Planetary Model

Early atomic model depicting electrons in fixed orbits around the nucleus, like planets around the sun.

Electron Cloud Model

Modern atomic model showing electrons distributed in a diffuse cloud, indicating probable locations instead of fixed paths.

Calcium (Ca)

Element essential for bone strength and other physiological processes; must be obtained from the environment.

Carbon (C)

Element with six protons; foundational to organic molecules and life chemistry.

Helium (He)

Element often used to illustrate atomic models; contains two protons, two neutrons, and two electrons in its most common form.

Mass–Weight Relationship

Concept that an object’s mass remains constant while its weight varies with the local gravitational field.

Atomic Mass Unit (amu)

Standard unit of mass equal to the mass of one proton or one neutron; used to express atomic masses.