Matter can also be classified based on their chemical composition. These are:
- Pure substances
- Impure substances
Pure substances are further divided into: Elements and compounds while impure substances are mixtures.
Matter can also be classified based on their chemical composition. These are:
Pure substances are further divided into: Elements and compounds while impure substances are mixtures.
A chemical element can be defined as a substance that exists in its simplest form and cannot be broken down by ordinary chemical process. There are 118 known elements. Elements are arranged in the periodic table according to their increasing atomic numbers. Elements are classified into three main groups. These are:
These are elements that donate their free valence electrons easily. Hence they are electropositive elements. They ionize by loss of electrons. Metals have a valency of +1, +2 or +3. They generally belong to Groups 1 to 3 in the periodic table. Elements with varying oxidation states between group 2 and 3 are called transition metals. Examples are sodium(Na), Potassium (K), Calcium (Ca), etc
These are elements that ionize by loss of electrons. They generally accept valence electrons to obtain stable electronic configuration state. They are electronegative elements. Non-metals generally have a valency of -1, -2 and -3. They belong to group 5 to 0 in the periodic table. Group 0 elements are called noble gases. Examples are Nitrogen (N), Oxygen(O), Carbon (C), etc
These are intermediate elements between metals and nonmetals. They are semi conductors of electricity. The
elements boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te),
polonium (Po) are considered metalloids. Astatine(At) can also be classified as a metalloid.
A great way to remember the metalloids is using: Boring Silly Goats Are At The Party.
| Metals | Metalloids | Nonmetals |
|---|---|---|
| Good electrical conductivity | Semi-conductors | Poor electrical conductivity |
| Solid at room temperature (except Mercury) | Solid or brittle solid | Can be solid, liquid, or gas |
| Malleable and ductile | Moderate malleability | Brittle and non-ductile |
| Shiny luster | Varies | Dull luster |
| High melting and boiling points | Varies | Generally low melting and boiling points |
| Regular crystal lattice structure | Mixed structures | Covalent or molecular structures |
| Low ionization energy | Intermediate ionization energy | High ionization energy |
| Form basic oxides | Form amphoteric oxides | Form acidic or neutral oxides |