Elements, Compounds and Mixtures - Video

Forty vocabulary-style flashcards covering atoms, elements, compounds, mixtures, symbols, formulas, and types of substances from the lecture.

Atom

The smallest unit of an element that retains the properties of that element; may exist independently or participate in reactions.

Molecule

The smallest unit of a substance that can exist freely and retain its properties; formed when two or more atoms bond.

Element

A pure substance consisting of only one kind of atom; cannot be broken down into simpler substances by chemical means; about 118 known.

Compound

A pure substance formed when two or more different elements combine chemically in a fixed proportion; has properties different from its elements and can be decomposed chemically.

Mixture

A combination of two or more substances that retain their own properties; components can be separated by physical methods; composition can vary.

Pure substance

A substance consisting of only one kind of matter (either an element or a compound).

Impure substance

A substance made up of two or more substances (elements or compounds) in any proportion.

Chemical symbol

A short notation (one or two letters) representing an element; indicates the element's name and one atom.

Atomicity

The number of atoms in one molecule of an element; monoatomic, diatomic, triatomic, or polyatomic.

Valency

The combining power of an atom; the number of electrons donated or accepted when forming a compound (e.g., Na +1, Cl -1).

Metals

A group of elements that are usually solids at room temperature (except Hg), lustrous, ductile, malleable, and good conductors of heat and electricity.

Non-metals

Elements that are generally dull, poor conductors, and can be solids, liquids, or gases; not malleable.

Metalloids

Elements with properties between metals and non-metals; semi-metals; examples include arsenic, boron, silicon.

Noble gases

Group 18 elements that are inert and very unreactive; examples: He, Ne, Ar, Kr, Xe, Rn.

Monoatomic molecule

A molecule consisting of a single atom (e.g., noble gases like He, Ne, Ar).

Diatomic molecule

A molecule made of two atoms; examples include H2, O2, N2, Cl2.

Triatomic molecule

A molecule with three atoms; example: ozone (O3).

Polyatomic molecule

A molecule containing more than three atoms; examples include P4, S8.

Rules for writing symbols

Symbols are the first letter (or first two letters) of the element; uppercase first letter, sometimes with a second lowercase letter; some Latin-name-based symbols exist (e.g., Hg, Cu, Au).

Berzelius system

System of chemical symbols introduced by J.J. Berzelius; the basis for modern elemental Symbols.

Alchemists' symbols

Historical pictorial symbols used to represent elements before modern symbols; not standardized.

Oxide

A compound that contains oxygen; examples include FeO, ZnO, CuO, CaO.

Sulphide

A compound that contains sulfur; examples include FeS, ZnS, CuS.

Chemical formula

Symbolic representation of a molecule showing which elements are present and their ratios (e.g., NaCl, H2O).

Molecular formula

A formula showing the exact number of atoms of each element in a molecule of a compound.

Water (H2O)

A compound consisting of two hydrogen atoms and one oxygen atom; a common example of a chemical formula.

Sodium chloride (NaCl)

Common salt; compound of sodium and chlorine in fixed proportion; widely used as a food ingredient.

Hydrogen chloride (HCl)

A compound formed from hydrogen and chlorine; diatomic molecule often discussed alongside acids.

Energy change in formation

Formation of a compound can release energy (exothermic) or absorb energy (endothermic).

Homogeneous mixture

A mixture with uniform composition throughout; components are not visibly distinguishable (e.g., air, sugar solution).

Heterogeneous mixture

A mixture with visibly different components; composition varies in space (e.g., sand and water).

Suspension

A heterogeneous mixture in which dispersed particles settle out over time.

Colloid

A heterogeneous system with very fine dispersed particles distributed in a continuous medium.

Emulsion

A type of colloid where both dispersed phase and dispersion medium are liquids.

Alloy

Homogeneous mixture of two or more metals with fixed proportions (e.g., brass Cu+Zn, bronze Cu+Sn, steel Fe+C).

Binary mixture

A mixture containing two components.

Tertiary mixture

A mixture containing three components.

States of matter

Matter exists in solid, liquid, and gas states; solids have rigidity, liquids have fluidity, and gases fill space.

Atomicity examples

Examples showing different atomicities: He (monoatomic), H2 (diatomic), O3 (triatomic), S8 (polyatomic).

Latin-name symbols

Some element symbols are derived from Latin names (e.g., Hg from Hydrargyrum, Cu from Cuprum, Au from Aurum).

Classification of elements

Elements are classified into metals, non-metals, metalloids, and noble or inert gases based on properties.

Oxides vs Sulphides (types)

Oxides are compounds with oxygen; sulphides are compounds with sulfur.

Symbol significance

A symbol stands for the name of the element and represents one atom of that element.

Elemental symbols (examples)

Common symbols include H for hydrogen, O for oxygen, Na for sodium, Fe for iron, Cu for copper, Ag for silver, Au for gold.

Molecule vs Atom distinction

An atom is the basic unit of an element; a molecule is a group of two or more atoms bonded together.

Fixity of composition in compounds

In a compound, the elements are present in fixed proportions by weight.

Solubility differences in mixtures

In mixtures, components may or may not be soluble in each other; in compounds, constituents are not separable by simple physical means.

Recovery of components in mixtures

Mixture components can be separated by physical methods without chemical change.

Element examples (naturally occurring vs synthetic)

Many elements occur naturally (e.g., Fe, O, Au); some have been synthesized in laboratories.